If there are no kinks in the rim, then it is likely that the wheel can be made true again. That involves fixing the bend while keeping the wheel round at the same time. It is best to remove the tire and tube while doing this. You will need a spoke wrench which is, fortunately, pretty cheap at the bike shops. You can do minor adjustments. Major adjustments call for skill and experience that I personally don't have. In that case, take the wheel to a bike shop and let a mechanic do it.
HTH