On this page of the game guide to Borderlands 2 you will find a detailed description of the side mission titled Statuesque. You can begin this quest during your first visit to the Opportunity location.
1) Bounty Board
2) Statue 1
4) Statue 2
5) Statue 3
6) Statue 4
Accept the mission , head to the first statue  and shoot at it. After a few shoots, Claptrap will suggest using the Overseer.
The robot can be found in the hangar . Approach it and activate with the button on the right side. Afterwards follow him while protecting him from the attack of Robots and Hyperion Soldiers, including a Badass Constructor.
As you return to the first statue  the Overseer will start destroying it and you will once again be attacked by a big group of enemies. Eliminate all of them and the Overseer will start heading to the next statue , where the whole process will repeat itself. However at the end you will be attacked by a Constructor.
By the next statue  there will be even more enemies, including a Super Badass Loader. The last one  will once again include a fight with a Constructor. If you manage to protect the Overseer and destroy all the Robots, approach it and once again press the button on its side. Wait for the robot to explode. Now you will have to return to Claptrap in Sanctuary to end the mission. Additional experience point can be gained if the Overseer will have above 50% health left after destroying all the statues.