Searching for 3D models for the game.

There are plenty of 3D models available online. Yes, most of them are paid, and yes, not all of them will fit the game's style, but that's a fact. Just Google it, preferably in English. If all else fails, you can create them yourself. It's quite simple: take a cylinder and apply a brick texture to it, that's all.
But what I'm interested in is this: how do you insert the model into the game? I've already done this in the fifth installment, but I'm not sure how to do it in the sixth part; I can only vaguely imagine the process.