I've read everything, and all i find is "activate that file in the plugin if you want to play that special game", but how can i do that ?
With ePSXe I just have to put these files (ex. SLES_029.66.M3S) in the patches folder and use the internal CDR plugin that will read it automatically
/me slaps his forehead.
PSXeven cannot do automatic M3S patching. However, PEOPs CDR will do manual M3S patching. For this you have to go to the config options for the plugin and select the appropriate M3S file.