Welcome to the board and welcome to the good guys
You will get smothered by information from the umpires on this board. Trust me, they do want to help.
However, the best thing you can do is go watch some good, experienced umpires from the stands. Just sit there and watch. Maybe make a note or two of things you see that you may want to try. When your team is practicing, get behind the catcher and practice along with them.
However, the key to becoming a good umpire is to understand that there are systems, mechanics and signals in place that have developed over the years. Nothing you learn OJT will replace attending some good clinics and a school.
Also understand that just because you've seen "Smitty" out there forever, it doesn't mean everything he does is correct. Longevity is not a synonym for good.
A quick starter for the plate. Learn to work the slot in a box toe-heel stance angled slighly toward the plate. Eyes at the top and outside of the strike zone.
Now, look out for advice from the rest of the gang here.
Good luck,