Hey m8.
Grab this (attached) sample mission; it will show ya ONE way to do it
Unzip to the following folder:
OFP / USERS / YourNAME / MISSIONS
<-----That one ...and load Desert Island + the mission named "Tanks Firing" :thumbsup:
There's a tiny scroll included in the mission folder - go read it matey
And just click on the triggers + the player's INIT to see the spells I used.
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Oh, forgot to mention...
the m60 tanks used here need 15 seconds to
load/reload a shell, so just be patient --- or use the game's timeBooster option