To make the app_config use notepad. Copy and past what bill wrote to notepad.
Under file hit save as, on the bottom set it to all files. Save it as app_config.xml
Put that file in the primegrid folder.
That is at under programdata then BOINC then projects then primegid.net
After you put the file there, in the BOINC mgr on top under actions(I think) click read app files.
Or close and restart BOINC