I was working on making a base for my build, but I realized that I do not know how to rotate the walls. Is there a hotkey for that? Do I have to make a separate part identical to the wall in a different direction? Help would be appreciated.

You cant. You should probably get BrickBuilder

I don't know what that is. But I did find a good alternative which was to swap the x and y axis using the size editor. And I will look into BrickBuilder once I finish my build.