How can I save my singeleplayer game in gmod 13 beta?

Hey guys. You see my question in the topic. I really searched for it. But all I found was, that I shall use the console commands gm_save and gm_load. But When I want to load like this, I got the message: second arguement is missing. When I wrote (gm_save first game) to save it under this name, than i got the message: error reading buffer.( I typed than: gm_load first game). So I really want to know how can I save my game!