Slitherine

I just started a paired game of ambush at sirte but do not really understand how to use the special units in the corner. Instructions say use the ambush unit selector to place minefields on the map. I selected the unit and moved the cursor to hexes where i would like to place but nothing happens. The unit itself cannot move out of the corner, so what do i do with it ?
Had similar trouble with the German equivalent which has text highlight "place convoy" if i move the cursor to the hex next to the unit (similar to the British) but when i press the unit itself just moved there ?. It too cannot get out of the corner and moving the cursor elsewhere just shows terrain details
sorry if its obvious to everyone else

Don't move the cursor, just place the unit on the hex you want. The Convoy and mines appear on the following turn.

Well i pressed enough buttons so it should be deployed somewhere but exactly where is anyone's guess. I suppose if i don't know what I'm doing at least my opponent won't either