How to add onagers to Rome Total Realism..??

I recently intstalled RTR 6.0 Gold, but unfortunately this mode does not have onagers...!!! what a disappointment...!!!:no:

I dont know why onagers are validates historical corretion, onager are used in those times however.

Anyway, I want to try adding vanilla onagers to RTR, and need your assistance.:yes:

Thanks in advance...