I have never played a race that can use mercs, but the process is the same. Firstly, have a read of this:
http://medieval2.heavengames.com/m2t...de/index.shtml
Pay particular attention to the middle of the articile where the parts of '
recruit_pool "NE Bombard" 1 0.4 3 0 requires factions { england, scotland, france, hre, denmark, spain, portugal, milan, venice, papal_states, sicily, }' are explained.
Basically, having look at your units (without having played them) , you need to delete
' and event_counter knights_errant 1 and event_counter free_company 1', and 'and event_counter knights_of_realm 1 and event_counter free_company 1'.
for the two units. Also, there is a faction requirement, which I am assuming you already meet. Lastly, with the knights of the realm, you will also need to change the 0.2 number to the number 1, as by mod design, you are never supposed to be able to build these, only replenish your existing units. All change to be made in the export description building txt file.