If you wanna play, you have to start up the webserver by clicking "Start PHP Server" (also make sure that the Apache HTTP is enabled through your networks firewall or else it won't initialize the server for you to join. After that, go to the "Host" tab and insert your rbxl map and setup your port. The Port number can be anything like "5005",  "9875", etc. Finally, go to the "Play/Join" tab and put the same port that you had in the host tab. Finally, click Host and wait for it to fully setup the server and then you should be able to join successfully. I hope this reply helps.