Well, I don't how you would read the music while marching holding a pair of cymbals. You'll need to memorize it. Take it in chunks. See if you can get a recording of the song and then see how the parts fit into the music.
Another way is to memorize it backwards. Literally, start at the end of the song and memorize a few bars. Then go back a few bars memorize those then then put them with the last couple of bars. This is how we did it in drum corps. It's a quick way of learning music. Good luck!
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Thanks,
Jeff Kozol
Author of Advanced Hand Cymbal Technique for Marching Percussion.
www.jeffkozol.com