You need at least 2 People and its very quick and easy:

Step 1: Player 1 opens up Matchmaking
Step 2: Player 1 selects a Deed and starts a vote
Step 3: Player 1 accepts but Player 2 does not accept yet
Step 4: Player 1 now physically moves to the map and opens it
Step 5: Player 2 accepts the mission now
Step 6: Player 1 now selects a quickplay mission with any difficulty and starts a vote
Step 7. Both players now accept the mission

Done

Please note that other people can't join you if you're doing it like that so you need to assemble your party beforehand.
Also make sure your lobby is private because other people trying to join your lobby will cause their game to crash.