For this achievement we will be using the Multifox add-on for the Firefox browser
. Install it and each new tab opened (ctrl+T) can be assigned a different profile by clicking the fox icon in the browser like so
Now you will need 9 tabs open all on different profiles, then go to http://jackbox.tv
with all of them and input the room code on your xbox screen. Once there are 8 players and an audience member in the game the achievement will pop, playing is not required.
Your screen should looks something like this