You'll be immediately given this mission after installing the core during "The Road to Sanctuary".
|Normal||True Vault Hunter|
|Gear:||Weapon Slot||Weapon Slot|
Lt. Davis will direct you to the city gates where you'll be allowed into the city. Your first stop is going to be to go into the garage almost directly in front of you. Inside, you'll meet Scooter who is a recurring character from Borderlands 1. He will tell you that Roland is missing but that the two of them had cooked up a Plan B.
Scooter will tell you to collect the two Fuel Cells in his shop. One is on the bottom floor on a shelf and the other is up stairs. Also make sure you search well for the Eridium here, you're going to need it. Eridium is an alternate form of currency that you can use to upgrade certain things at the Black Market in town (such as ammo and backpack capacity).
Take the Fuel Cells and Eridium to the center of town. There's a couple of sockets in the ground. Place the two fuel cells in to the two sockets in the center of town, then you'll have to track down Earl who is another recurring character in Borderlands. He runs the Black Market in town and will provide upgrades for you. Buy any of the upgrades from him and he'll toss in the Fuel Cell for free. Take the last Fuel Cell to the center of town and put it in the only remaining socket (should be marked on your HUD).
Scooter will direct you to Roland's House/Command Center HQ. When you try to enter, one of the guards will call you over and give you a key. Enter and pick up the Audio Recording directly in front of you.