When you have the flu and are experiencing body aches you could lay on a heating pad, use some hot compresses such as hot water bottle.
You can also take a hot shower and the hot water can help with the body aches which it always does for me and the hot shower helps to wash away the germs from the flu to help you feel better as well.
Or soak in a hot bath as the soaking in the hot water can help with body aches from the flu as well as back pain or any other muscle aches.
Taking Tylenol or other pain relievers such as Aspirin or cold and flu medicines can help alleviate body aches from the flu.
Within a few days to a week though the body aches with the flu should go away even without any treatment.
You can provide temporary relief from the body aches from the flu but you can't really make them go away fully and that just takes time for the body aches to go away fully.