You can play it in any way. If you want to play it with gmod, make sure you have a friend, start a peer-to-peer server, and let your friend join. And make sure your gamemode is set to prophunt. However, if you want to do it with a dedicated server, create a server, and in the batch file, look for "+gamemode sandbox" (Without quotations) and then replace sandbox with "prop_hunt" (Without quotations). Hope this helped!