Just place your unit on the map.
Then put something akin to this in his init field:
hunter setpos [getpos tower select 0, getpos tower select 1, (getpos tower select 2) +5]
hunter would be the name you give the unit, tower would be the name you give the tower, change them to the correct names you have used.
The '+5' you might have to experiment with this till you get it right, it is the height.
Syntax almost quaranteed.
Planck