You need to take the .mdl file you downloaded, being bardok, and replace a character in the mod with it. go to sierra/half-life/esf/models/player and find the character you want to replace, and put the bardok.mdl file in there, and name it as the char your replacing. Example, i want to replace goku. I go to the goku folder, and i put the bardok file in, backup the goku model, and then name the bardok file goku.mdl
That should do it