right first off, .pk3 file can be opened as .rar or .zip are, in other words use programs like winrar etc. then drag the folder ' model to ur trem/base. then just put all the models in there that u want to use. ps its easyer l8er on if u put them in folders ie trem/base/models/gamemodels/rifle.
this is how i work but u can do things differenty if it sites u.