Chapter 5: Plan B - Borderlands 2
Approach Pvt. Jessup at the gate then talk to the town mechanic. Simply approach the markers to find Scooter. Take the eridium from him and pick up the two fuel cells in the garage.
There are also optional missions available for you; simply head to the exclamation points in the map and talk to the NPCs under them.
Rock, Paper, Genocide: Fire Weapons! - Marcus Kincaid
Rock, Paper, Genocide: Shock Weapons! - Marcus Kincaid
Rock, Paper, Genocide: Corrosive Weapons! - Marcus Kincaid
Rock, Paper, Genocide: Slag Weapons! - Marcus Kincaid
The Name Game – Sir Hammerlock
Assassinate the Assassins – Bulletin Board
There's also an NPC named Michael Mamaril standing outside the hostel. Talk to him to receive a random weapon.
When ready, head to the plaza and lift the first hatch then install the fuel cell there. Do the same for the next fuel cell.
Next head to the Crazy Earl, a special shop that sells rare, unique upgrades that can only be purchased by Eridium. Buy something there to get the third fuel cell. Install the third fuel cell to update your mission.
Next, head to the Raiders HQ and talk to the raider outside to get the key. Enter the HQ and examine the Echo recorder on the table to complete this mission.