Gamer has been removed
This is part of the Operation Broken Eagle DLC.
You will need to go to Central City and clear the stage near the Museum. This is where you will get the GPS Tracker. Now, leave Central City and head to the Mayor's Mansion in north eastern Sunset Hills and clear out all of the soldiers. Go to he back yard, head inside the mansion, go upstairs and get the key to the President's Room from a secret service agent near the door. Once you secure the President, the DLC will come to an end.
Note: All of these achievements in this DLC need to be completed prior to going to the Mayor's Mansion. After that point, you will not be able to obtain these achievements and you will be required to start a new campaign to do so.