@Rome-Li what problems are you facing? I haven't tested the plugin but, the more information you can give here on the community, the more likely you can get help here.

It is better to do that from the admin control panel. But if you don't have access to the ACP. hget group:gid administrators "1" <- use this value sadd gid:1:members <uid> replace <uid> with your user id. To get the user id use : hget username:uid <yourusername>