Gotta do 2 things.
First you have to make sure the unit has the appropriate faction skin coded into it;
Code:
type barb_archer
skeleton fs_fast_archer, fs_fast_dagger
indiv_range 40
texture dacia, data/models_unit/textures/unit_barb_warband_archer_dacia.tga
texture scythia, data/models_unit/textures/unit_barb_warband_archer_scythia.tga
texture slave, data/models_unit/textures/unit_barb_warband_archer_slave.tga
model_flexi data/models_unit/unit_warband_archer_high.cas, 8
model_flexi data/models_unit/unit_warband_archer_med.cas, 15
model_flexi data/models_unit/unit_warband_archer_low.cas, 30
model_flexi data/models_unit/unit_warband_archer_lowest.cas, max
model_sprite slave, 60.0, data/sprites/slave_barb_archer_sprite.spr
model_sprite scythia, 60.0, data/sprites/scythia_barb_archer_sprite.spr
model_sprite dacia, 60.0, data/sprites/dacia_barb_archer_sprite.spr
model_tri 400, 0.5f, 0.5f, 0.5f
If your faction isn't there, just copy one and paste it, then only change the faction name.
And then add it to the building you want it recruited from;
http://forums.totalwar.org/vb/showth...uide-%28WIP%29
Hope that all makes sense.
Good Luck.