Hi Henry,
welcome to FISD!
It's a bit more difficult for taller people to find a reasonably good-fitting suit of armor. However, it's not impossible.
Good luck in your journey!
As a first step, you would need to apply for 501st TK status. Look here:
Then take a look here at the checklist; a few pictures are still missing. You also have to apply for Expert Infantary first. Then you can submit a Centurion request.