you dont really need top, all that matters is that is the primary frequency is tuned to the secondary frequency, by adjusting the primary to match,
you need tools to tune it, preferably a scope and a wave generator.,,
but I have a feeling that is not an option, so this may work...:
RMCybernetics - DIY Homemade Tesla Coil Tuner
but i have never actually tried it
either way tesla coils are dangerous, and i would recommend reading the safety guides first
I like this guy,, he keeps it simple:
Trashy Tesla Coil a tesla coil made entirely from junk from dumpster diving