This will take a total of at least 3 sessions. Play as each of the below new characters:
The Influential Governor
The Resilient Highlander
The Fearsome Coyote Man
This can be done in any mode, and solo in Wolfpack if you want. Just choose one of the 3 characters included in the DLC and play one session. You cannot quit out early. If you aren't unlocking it, you may want to recheck the characters you picked. Some of them look similar. If doing Wolfpack, enter the session and just let the time run out.