The white part is like a train track. it guides the cutting blade . and also provides a smooth slide surface for that cutting blade. itgoes in between the cut blade and outer guard. . put the cutting blade on the clipper drive, then the white guide, and then place the outer guard on and line it up with the screw holes. then screw away! :)

RTM. Read the manual. You can find the manual on Google with your make and model. Are you sure you are also using the correct blade?