Easy achievement that took just a few minutes to complete.
*The other solution above is sufficiently explanatory but here is another, to add context for those who have never looked at the game before, and want to get this done ASAP.*
1. From the Main Menu go down to XBOX LIVE and select it
2. Now choose PLAYER MATCH and then CREATE ROOM - you can change the settings to "Invite Only" if you want, but you don't have to
3. Now simply hit A to create the room
4. After it loads, hit B and go up on the Analog Stick and then A again to leave the room
**(If creating a room starts to lag out indefinitely, see below for how to fix it)*
5. Repeat this 9 more times (from the CREATE ROOM screen - A, *room loads*, B, UP, A - repeat)
**I had an issue when trying to create my 9th room where it would hang indefinitely. Going back to the Main Menu, and then returning to XBOX LIVE, creating a RANKED MATCH, and then exiting and returning to PLAYER MATCH fixed this for me. This seems like a rare fluke, but I wanted to include how I fixed it, in the case that it happens to someone else. I am sure restarting your Xbox or the game would fix this also.