ᐅ IKEA Förhöja wall shelf with drawers, used, assembly instructions included

Hello, I bought a used FÖRHÖJA wall shelf with drawers and the one with bins. Now I'm wondering about the best way to attach it under a wall cabinet. Not to the wall itself, but to the wall cabinet, because the previous owners of the kitchen also mounted their FÖRHÖJAs there, and the holes are already drilled. Should I use just screws? Or screws and nuts for extra security?

Hello, follow the instructions as described.

Thank you very much! Let’s see if I can make sense of this. 😕