Please find a short version of the configuration instructions within "UPX Addon.ini" .
Once this add-on is activated, any EXE or DLL will get compressed / packed automagically, right after the compiler finished creating them, and a notification of either "success" or "failure" in compressing will be issued to the (compiler-) user .
Please view the screenshot below for further information.

UPX Addon v.1.5.8.28