How do I get my Start Page and Project explorer not to be individual pages?

It's a basic drag and drop solution. 
Just click and hold from the top part of the project explorer and drag it to the left side of the screen and drop it right there.
Once you start dragging, you should see blue arrow icon on the left middle side of the screen. Just drop it on top of it.

Just to add, see Docking. Via menu,  disable Tools -> Docking Allowed and View -> Desktop -> Restore Default Docking.