Help - Cardboard in-cab tank cover install

[demi]

Hi all, Could someone explain to me how this crappy thing is supposed to fit in the cab.
How does this thing attach or does it just sit there looking like crap. Where are those three tabs on top supposed to go



Also, I want to use the carpetted tank cover, and I was wondering if this cover comes pre-molded to a new piece of cardboard or do I have to use this cover shown in the pic.

Any recomendations as to who sells the best quality cover?

Thanks,

demi