First I have a few questions:
1.) Is the program made up of the two modules?
2.) Are either of the modules in the service program?
3.) Does the program have its own code and it just uses the two modules and they are not in the service program?
If the answer to question 1 is yes, then make the changes to the modules, compile them and then issue the UPDPGM command.
If the answer to 2 is yes then, make the changes to the modules, compile them and then issue the UPDSRVPGM command followed by the UPDPGM command.
If the answer to 3 is yes then make the changes to the program, recompile it. If, for some reason, you created the program with the CRTPGM you will need to issue the UPDPGM command after a successful compile.