Once you get the Chapter 4: "Got Your Goat", you will unlock the "crowbar" that opens up fast travel for you in the game.
Afterwards, head to any of the other maps and look for a sewer hatch and go into it. I recommend the one at the Mini-Market as the others you might not be able to finish as you might need future story abilities.
Reach the end of that room and you will unlock fast travel between Becky's House and that new area. Also unlocking this achievement.