After you have installed the required update and downloadable content, you must complete the mission "My First Gun" in Windshear Waste, if you have not already done so.
After completing this mission, 'Hunter's Grotto' will appear in the Fast Travel System.
Please note the first mission of Sir Hammerlock's Big Game Hunt, "Savage Lands", is suggested for characters level 31 and higher on Normal Mode and level 35 and higher on True Vault Hunter Mode.