Just train train train. Try to find out what works and what doesn't. It took me until my 3rd year, which was 7th grade to win, and I only won because he talked smack so the ref counted slower when he got me to my back which let me get up and win by points. Since then I have won plenty of matches, but you'll still lose some, but just find out what works for you.
Assuming you're in shape, learn your moves and drill drill drill drill. You need to be learning outside practice. There are no shortcuts in wrestling its one of the most technical sports there is.
I went to a tournament and was in two matches. I got pinned on both matches and in both at the first round.
Im asking this in the wrestling section also, just thought some martial arts would have bound to be wrestlers also