Not exactely sure what you mean, but if you have found a script and want to use it in your missions then you need to place the .sqs file into your mission folder then have it activated by a trigger or a init field.
Like this for the init field:
this exec "evac-chopper.sqs";
this can be replaced by whatever name you have given a unit etc.
By placing the .sqs in your mission folder I mean like this:
OperationFlashpoint/User/YourName/Missions/mission-name (or something very close to that)
Des, OUT!