On this page of the game guide to Borderlands 2 you will find a detailed description of the side mission titled The Overlooked: This Is Only a Test. You can begin this quest in The Highlands after the completion of the side mission named The Overlooked: Shields Up.
The Highlands - northern part
The Highlands - southern part
2) Robot camp
3) Mortar panel
Accept the mission from Karima  and head to the southern part of The Highlands, to the Robot camp . Fight your way to the other end, where you will find the panel from the above screenshot . Use the button on the left side of the panel, set the coordinates and shoot. After the training round, input the new coordinates and shoot again. Now you can return to Karima and collect your prize.