I'm assuming you want to bebug an ILE RPG program. The first thing you need to do is ensure you have keyword DEBUG(*Yes) in your H-spec(s). Next step is to compile your program with the debug parameter of your choice (My preference is *ALL). After that, all you have to is use the STRDBG command. STRDBG will present you with a listing you can then set breakpoints for. Once you've set your breakpoints press F3 or F12 to exit. Now execute your program. It's that simple.
Use all the steps mentioned above, except step 1, to debug ILE CL programs.