MX Simulator

Hello everyone, i am coming across a problem i can not seem to get around and need a little help. I want to start to try skinning and messing with it and i did a bike and everything turned out fine. However i got to the gear and made the saf correctly (i think). The problem is i do not know how to change the player model. Considering the player model for the gear has the neckbrace. I downloaded the player model but do not know what to do with it. Sorry for asking and now knowing how to get over the problem. Any help would be appreciated

Thank You.