How do I get a 41 overlay working?

[Orome]

How do I get a module overlay to work so that the indicated operations from the corresponding installed module are preformed when I press a key?

For example I have SANDMATH-IV in Port 1 on a 41CX (emulator) and I want the corresponding overlay to invoke SANDMATH-IV operations. How do I get that to happen? I understand that I can type in function names manually (and that I can identify what's in loaded modules using [CATALOG]), but I don't understand how to get the overlay working.

How do I do that for SANDMATH-IV? Is there a particularly way to do it generally, or is that different for each module?