Then you change the master_prpcclient.ini file and include all the information like email and stuff and in the line where [// server= configures the mix of work to perform across one or more] is you should replace that with the exact line
when you have saved the master_prpclient.ini file you click on the 8-oct-update-prpclient-ini.bat and that will copy your master ini file to all the folders you made earlier.
When you want to start the prpclient you then click on the 8-oct-start-prpclient.bat and that will start 8 cmd prompts. You can shut down 1 or more if you want to for example just run 7 if you need 1 core to feed your gpu for other program.
Lastly this particular program (the 121 prime search) doesn't have a gpu program so it is cpu only.