You have to braid the stems while they are young and pliable. Your plant will never be a braided stand up plant. It wants to be floppy. You have to go with that growth habit or get another plant.
Cuttings root very easily.
To prune, decide what shape you are going for and prune off the excess. When you are happy with the results, cut another 2 or 3 inches off each branch. New growth will be at the nodes at the ends of the branches so you need to cut beyond what you are happy with so you will be happy with it when it starts to grow.
Rooting cuttings:
Method 1: take cuttings, peel off all the leaves except for the top 2 or 3. Put them in a jar of water. Add a couple drops of Hydrogen Peroxide everytime you change/add water. The Hydrogen Peroxide oxygenates the water and helps the cuttings root more quickly.
Method 2: Take cuttings, apply rooting hormone to the base, poke a hole in the soil with a pencil and put the cuttings in the holes. Be careful not to knock the rooting hormone off. Water to snug the soil around the cuttings.
Wait..............
Personally, if you have the room, I would leave it alone. I like it.
Daisy