Being that the flu is a virus, there is no way to kill it; you have to let your immune system do its job. If you're looking to support your body while it hunkers down for this difficult task, you'll have to drink LOTS of fluids; no caffiene or alcohol, as they can dehydrate you and force your organs to work harder than they should be when your system is already compromised.
Take vitamins; you cannot overdose on vitamin C, so take as much of it as possible; I suggest one pill per meal.
If you don't want to go nutso with specialty vitamins, then take 2 of your regular daily vitamins when you wake up, and 2 before you go to sleep...do this every day until you're feeling better.
Get NO LESS than 8hours of sleep at night; our immune systems repair themselves while we sleep, it is absolutely imperative that you sleep as much as possible when you are sick; if you can't nap during the day, make sure you go to bed early enough at night to allow for a full 8 hours.
Make sure to eat; sometimes the flu can wreak havoc on your appetite. Don't forcefeed yourself, but make sure you're getting at least 1200 calories a day, and keep it healthy. Healing takes a LOT of energy, our bodies can't work if we don't give them the proper fuel.
And finally, wash wash wash your hands. You don't need to pick up any more bugs while your immune system is compromised.
Good luck, and feel better!!