Once you've downloaded and setup your center on our site, which you can see how to do here, open up the downloaded file in Roblox Studio and publish it to either your profile or group, depending on where you want the game to show up.
Now click Game Options on the top bar in studio.
Then click on the side bar to security and enable the option, "Allow HTTP Requests"
Then click save in the bottom right.
Now publish the game again with Alt P or Option P!
Now if you go to the Roblox page for the game, click the three dots next to the name and click "Configure Place" and then go to access.
From here you may want to change who can enter the game including game size and group access.
You're now all set to receive applications!