Loading and unloading infantry from helicopters in OFP has always been a little poor. Basically the helicopter has a LOAD waypoint, I like to put that right ontop of where the chopper is on the map. Sometimes this will cause the chopper to rise in the air as if going to the waypoint then land again in the same spot. The soldiers need a GET IN waypoint. Syncronize the helicopter's LOAD and the troops GET IN. Sync is F6 I think. Lastly at the landing Zone place an Invisible H on the map. Empty > Objects. On the H place a TRANSPORT UNLOAD waypoint for the helicopter.
That is basically it. Depending on the terrain the helicopter may have problems landing on the H but will try anyway which can result in crashes.
You can also start the soldiers loaded in the helicopter if you like. Name the helicopter something like Chopper1. In the Init line of Each soldier type
this moveInCargo chopper1