Note: You have to trigger the medal opportunity message in order to be awarded for this medal and for this achievement.
Warning: Make sure to save your game before you approach the Town Hall (last building) where the Panther tank will break through the right wall. If you fail the objective, you will have to restart the mission or reload your saved game.
On mission 5 "Assault on Rochereau", after you capture the Motor Pool building, there should be a breakable wall facing the corner of the Motor Pool building.
After you break the wall near the Motor Pool building, there is a road with an allied tank. After you approach the allied tank, a message should pop up: "Medal opportunity / Capture a Panther tank so the Allies can examine it."
When you reach the last building, stay outside of the driveway to avoid summoning the Panther tank. Now, place a machine gun nest in front of the Town Hall, which will distract the Panther tank. Press Y to bring up the destruction and demand menu, select the machine gun nest icon between the 4 o'clock and 5 o'clock position, press either A or X for the .30 or .50 cal machine gun nest, and then move and press A to place it on the ground on the side of the drive way, near the low fence.
Next, you will need a tank to initially protect yourself. Steal or purchase a tank and then enter the tank as the gunner so that you can jump out easily. While in the tank, rush towards the side of the Panther tank. Quickly jump out of your tank, and run towards the side of the Panther tank. Press X once to hijack it. If you press X two times or more, you will hijack the tank but then jump out.
When you complete the mission, you should be in the Panther tank.