What i have to do is to drive the car equipped with the rims to the parts shop then Alt-tab to the trainer. Take for example this scenario, I wanna snap on some rims that I managed to install on a normal car in my safe house to my M3.
It includes some parts manipulation functions that can be used to modify certain cars with visual parts you can't get in the parts shop.
This is the new version of the Mega Trainer.