Welcome Mindi/ I upload photos here to post all the time. In fact I have no photos stored on my laptop so they only come from my phone.
1) At the bottom of the post, click on the option "Upload an image".
2) My phone shows the most recent photos I have taken. Or I can click on the "hamburger", the three lines at the top left for more choices of where my photos are stored, like the 'Gallery' on my Android.
3) Choose a folder or photo. click "Open" at the top of the page.
4) Dave has already programmed in a photo link for your and it will show up as "lightbox".
5) At the bottom of the page it allows you to "add another photo" , click on that if you want to share more photos and follow the same order above.
Hope this helps!