Your link is bad, but just make sure you have this in the helicopters init
Heli1 flyinheight 85
Make sure you have 2 way points on your helipad (Loacated under empty-objects in the editor)make the 1st waypoint on the pad a load/unload. the second way point make a move waypoint right next to the unload/load one. In the onact of the first waypoint type.
dostop heli1; heli1 land "land"
In the Condition of waypoint #2 Type this for player1 and player2 (these are your unit names you want to board the helicopter, they are interchangeable with your own valid unit names)
((!Alive player1) OR (player1 in heli1)) AND ((!Alive player2) OR (player2 in heli1)
this causes the helicopter to move after those 2 people are in the chopper
Try this video for help, if you need an example mission let me know i might be able to scrub one together tonight.
Hopefully this all works, like I said the link to your mission is broken and you may want to use a diffrent site because the website your mission is posted on is red flagged for malicious software usage
whoops sorry, just realized this is for ArmA not ArmA 2, give her a try though they may be similar. (I spent all this time typing just to find out that you have the original arma, lol)