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How To Install a mod for ArmA.
You should first read the background for OFP mod installing.
On top of that knowledge, you should also read the usage of -profiles parameter (mod dir stuff).
After you have downloaded VTE archive, you should download the Extended Event Handlers (XEH) archive too. You should put XEH into its own mod dir and VTE its own.
When you have unpacked all the first, run ArmA with a command line to point into these mod dirs, for example like this:
arma.exe -mod=x\xeh;x\vte -nosplash -world=VTE_intro -profiles=d:\ArmA