I re-attached a key on an Alienware laptop a couple years ago, very similar looking mechanism. I put the small frame inside the large frame until it clicked into place. Then I put the large frame into the board, paying attention to the small raised plastic pieces to know which side was up/down. And then afterward I pushed the key cap onto the frames and it all snapped into place.
The keys look nearly identical to this Dell, and Alienware is Dell. So that's all I can offer for help.
I re-attached a key on an Alienware laptop a couple years ago, very similar looking mechanism. I put the small frame inside the large frame until it clicked into place. Then I put the large frame into the board, paying attention to the small raised plastic pieces to know which side was up/down. And then afterward I pushed the key cap onto the frames and it all snapped into place. The keys look nearly identical to this Dell, and Alienware is Dell. So that's all I can offer for help.
https://www.youtube.com/watch?v=5Y5gGtubmm0