What do I need to know about this?
There isn't really anything new here - we are applying things we just learned (SAS, SSS, ASA, and AAS) and things we have learned before to solve problems.
This doesn't mean these problems are easy, though. You will have to think creatively, try various things, and check your work carefully to write accurate and complete proofs.
Let's do the first proof on your work as an example:
Complete these proofs for a 3!
Try this problem for a 4: