You have to set up remote coverage.
do a "change coverage remote, and set up the number you wish to dial out to, including the 0 or 9 or whatever you use to dial an outside line.
Then on the coverage path of the station, point it to the position you just programmed, so if you put it on position 10, put R10 on the coverage path.
Also make sure that you have rights enabled in COR etc to allow forwarding outside again, if you want external callers to be forwarded..
Hope this helps
Rob
Rob