Metal Slug X - Mutliplayer Achievement Help (shouldn't take more than 5 minutes)

Hi, I'm looking if someone could help me out with the Metal Slug X multiplayer achievement. I only requires you to play with someone online and will unlock at the start of the game (hence it shouldn't take more than 5 minutes). If you own the game it installs very quickly since it's a very small game (a few megabytes). Your help would be greatly appreciated ;)