How do I make it bushier ? Where should I trim?

You have 2 options. You can pinch the center out of the growing branches and hope it forces back-budding lower on the stem (below existing foliage) so you can cut back to that growth; or, you can simply cut the stems back to a node just above the soil line and wait for the plant to back-bud. Unfortunately, how enthusiastically a plant responds to pruning depends in large part on how much stored energy the plant has at the time it's pruned and its current ability to carry on photosynthesis. Your plant has very little in the way of stored energy and appears as though it needs much more light than it's receiving.

When plants lack access to a full compliment of nutrients or it is suffering deficiencies of one or more nutrients, they are genetically programmed to rob nutrients and other essential bio-compounds from older leaves, then sheds the leaves from which the nutrients came. Nutrients aren't plant food; rather, they are the building blocks plants use to put on new growth and an essential part of how they keep their systems/processes orderly and balanced.
* When is the last time you fertilized?

As noted, you can pinch, but by looking at the plant we can see it's a sure bet the response will be lethargic. What makes the most sense is to review your care regimen and see what's holding the plant back, fix that, then start thinking about pruning/ pinching as a method of increasing ramification (leaf and branch density).

Some "pinched" plants:
coleus:
lightbox]2023-08-11/tapla/c94877[/lightbox]

coleus:


aeonium:


4 species of mint:


pilea:


Al

agreed, essentially, your plant doesn't look happy enough to branch on its own, so pinching isn't going to make it happen either.

I actually never fertilized it… i'm a plant newbie. Sorry. Don't really know what I'm doing. I just give it water. I used to put it by the window but I think that was too much direct sun so it burnt the leaves a little. And the pot was too big, So I don't put it under direct sun anymore. And transferred it to a smaller pot. But it's still not happy…Any suggestions on how much sun? What fertilizer should I use?

Hey, we all have had our learning by mistakes! At least, I have!

Here's what I think: Discard this, Get a new plant.
As a newbie, trying to rescue a plant that has become small and weak is going to frustrate you.

If you want a plant for a very sunny windowsill in CA, there may be better choices.

Hello Zoy,
Welcome to the forum and the world of houseplants!
To a certain extent, growing houseplants is a matter of trial and error.
That said, I'm glad you're here looking for advice. There's a lot of information here that can help you succeed. It's a really rewarding hobby when you get going with it.
I find it helpful to look up the native habitat and natural growth habits of any plant I'm trying to keep. As much as possible, it really helps to try to match the plant's requirements to the conditions you can offer.
Basic factors are: light, pot-soil-watering (these are all related), temperature, humidity, and fertilizer.
The plant you have is not happy with the conditions it's in. I suggest you continue to try to adjust things to improve it, but you might also try another plant that is better suited to what you can offer it. Some are easier than others.
It's great to be new, just starting to learn about all this, and open to suggestions. We all started someplace, dig in!

I actually never fertilized it… From the plant's perspective, that's a problem. All but a few terrestrial plants well-adapted to spare (low resources) soils need a regular infusion of nutrients from fertilizer. The nutrients in fertilizer shouldn't be thought of as plant food. They aren't. Nutrients serve as the building blocks from which new growth is assembled, and as well are essential to the balance of plant processes and systems. A plant's real food and energy source (not considering the sun) is glucose, a sugar made during photosynthesis.

Unfortunately, your plant has only enough energy to remain viable. Cultural stress factors create imbalances that prevent the plant from realizing as much as and arguably more than 100% of it's potential in terms of growth and vitality (health). How can I tell? When a plant is making exactly as much energy/food during photosynthesis as it uses/burns during the respirative stage, it is said to be at its LCP (light compensation point). If the plant created more food/energy than it uses, it needs space (cells) in which to store the excess energy, so it grows. If it is unable to create enough food/energy to reach its LCP, it's systems and processes will inevitably become unbalanced to the point of failure/ loss of viability. Your plant is right in the gray area where it's not precisely clear if the plant is making more or less food/energy than it's using. Your job is to turn things around.

This might help: The thread "An Overview of Good Growing Practices" in Houseplants forum

Sorry. Don't really know what I'm doing. I just give it water. Watering, how/when you water, is an art in and of itself. Getting to the point where you can water as copiously as you want without concern you might over-water is an enviable place to be for all who grow in containers. There is more info about watering and soil choice in the link provided.

I used to put it by the window but I think that was too much direct sun so it burnt the leaves a little. I explained above what a plant's LCP is, but I should also say plants vary by species when it comes to how much light they need to not just remain alive, but to thrive as well. Your plant will take a lot more light than you think it will indoors, but it doesn't like full sun and it has to be acclimated gradually to a higher light position. The key is to give your plants all the light they need, but not so much it damages foliage or the plant's photosynthesizing machinery. Consider light a key issue.

..... it's still not happy…Any suggestions ..... What fertilizer should I use? Overall, you would first want to flush the soil next time the plant needs water, which should flush out most of the dissolved solids in the soil, effectively resetting the soil's fertility level to 0, then fertilize. There is no question the plant is nutrient-deficient. Foliage-Pro 9-3-6 is a super fertilizer for nearly anything you might grow in a container.

If you have additional input/ questions ..... don't hesitate.

Al