2001 Rec Center Dr. should get you to the field location.
If you're coming in from 79, you'll come up Mon. Blvd make a left at the coliseum and head down Patteson Dr. At your first opportunity to turn right, do it onto Morrill Way. Then follow a detour sign to make a left down the next street. Follow this until you pass the fields on your left and go through the two stop signs. Then park anywhere in the parking lot.
Alt route: Continue driving down Patteson until you make a right on Rawley Ln in between Qdoba and Kroger where you will continue up the hill until you see the fields on the right and make a right into a gravel lot towards the tennis courts and then another right to parking and walk a short distance to the fields.
Taking I68 in is also an option but with multiple exists to take you different ways, it is harder to give you turn by turn directions. Best bet would be to aim for Patteson Dr. or the Coliseum and then follow the I79 directions from there. Also, feel free to ask me for help or call if you get lost.