how do i activate mercs in sector?
Press D with your coin merc.
Are you using a coin merc.
(http://i54.tinypic.com/35d3jf5.jpg)
make sure the coin merc is on the "sector mercenary" slot.
You can only do that with coin mercs. Press 'D' to spawn a merc. However, if there is a gap that must be jumped over (as in map 153 for example) mercs will stay at the other side untill you press 'D' again to teleport him to your side of the gap.