The plates are comprised (mainly) of two sets of pieces: the main part, and the negative part. The negative parts can be added to the main parts using super glue (or hot glue).
Here is a run through of the various plates that you can add to your Buddy 4000 to dress it up.
Foot with negative pieces
Head-Side Plate goes on the side of the head.
Back-Plate goes on the back of the main body.
Head-Front-Plate goes on the front of the head (duh)!
Front-Plate goes on the front of the main body.
Head-Top goes on the top of the head.
Body negatives go on the sides of the Body-Front pieces.
And that's it!