referencing the player

recently, i've been trying to do several things to the player(heal, change weapons, change speed, etc.) and recently saw this snippet of code that would make it all easy.

dirk.mountimage(machinegunimage, 0);

the problem is, i am not sure how or where i would name the player dirk. also, if its possible to name him different things, for multiplayer, that would be helpful too. my grasp on torsion code isnt great, so code would be helpful. thanks in advance