Head to the marked location and talk with Sam. Drive to the fuel depot and take out the enemies before planting the explosive inside. Sam will cover you with the .50 cal but you need to help him as well since he has a life bar that regenerates slowly. There are heavies in each area so it will be a good idea to kill them using high explosives like the C4 or RPG. After planting the explosives get out of the depot and wait for it to explode. Drive to the next depot and do the same for the other three fuel reserves.
Now head to the maintenance building and take over the mounted machine gun while Sam does his job. There are explosive barrels in the area that you can trigger and help you clear the area faster. Once done, continue killing the enemies as you make your escape. After leaving the compound, your mission will be completed.