Some simple points.
1) You cannot assign waypoints to an empty vehicle.
2) You must ensure that the getin waypoint is "attached" to the empty vehicle: place the waypoint right on top of it. You should not be able to move one without the other: in fact, after placing the waypoint, you will have to press and hold the SHIFT key in order to edit the vehicle.
3) The scripting commands that have been quoted in this thread are all excellent and sometimes the only way of getting what you want. However, before using any of them, you should understand the waypoints - waypoints and triggers are the basis of all OFP mission editing.
4) snYpir wrote many excellent tutorials and if I could give one piece of advice to all noobs it would be to read all of them. Don't worry about not finding this one for now, it doesn't cover this problem in detail.