The best you can do is get to some lessons. Even with a good book or internet you can't watch a fly being tied and that is the real learning. After a few lessons you will be able to tie any thing you see or dream up.

Three flies to learn for the Park are:

Thunderhead dry fly taught by Walter

Georges Nymph Fish these two together and you won't have a fishless day.

This one is a variation of the Wooly Bugger No. 12 standard hook, olive green Maribou tail twice as long as shank, 6-7 wraps of lead wire. olive green dubbing, finished with two pieces of crystal flash on each side and out into the tail. Give it a good thread head. This fly is deadly on bass and blue gill, and sometimes produces on tail waters