Generally speaking, you back a bow by gluing a layer of something onto the back. Getting a good glue joint requires even pressure if using another wood (sinew is a different matter.) The thickness of the backing and the clamping technique you use are variables.
Also generally speaking, tip overlays are made of something harder than the bow wood itself so the repeated action of the string doesn't harm the bow. Sometimes they're necessary (if you use the Fast Flight strings, or so I've read) but they are often added to embellish the bow and even to add a slight recurve. What they're held on with depends on what they're made of. If you join wood to wood, wood glue is fine but if you join horn to wood (two different materials) you'll want something more like epoxy.
As for making this complicated, there are about twenty variable all working with/against each other all the time so each bow has to find its own balance. The shooters found their balance of shape, materials, forces, etc. whereas the more numerous pieces didn't. It is what it is so my advice is to start making shavings and start developing your experience; you ain't makin' if you ain't breakin'.
Good luck and post pics as you go; these guys are great at helping you progress.
Joel