While your monitor is on the vesa mount, slightly unscrew the two screws on the side you're planning to attach the vesa mountable arm. In my case, I have the top right and bottom right screws.

Slide in the vesa mountable arm. If needed, unscrew the screws a bit more.


Use provided screws: M4x16 or M4x20
If your monitor vesa mount is slightly inside the monitor(indented), you could do one of the following: