A simple way to do this achievement is to push Start, go to Game Lobby, and the list will refresh with people who are in the same chapter/location you are in.
If you succeed in getting into a game, stay there for 15 minutes and a progress bar should come up. If your in a group with 3 others, it should say 3/10.
Sometimes you cannot join a random persons lobby if their name is in red text so your best bet would be to go to the main game menu and click Play, then it should say to push one of the buttons to go search for a quick match (or something along those lines) and you should be able to jump into a game that way.
I hope this helps!