Take it to the nearest auto body repair shop that has a frame straightener ...

The difficulty that arises with bent tools is that when steel, the usual material, bends, it also hardens most (called work-hardening) where it bends most. When you try to bend it back, it's most likely to bend most somewhere else, where it has not been previously bent, since the original "unbent" material is slightly softer than the material in the original bend.

With practice, one can learn how to compensate, but you're unlikely to develop the skill to a high level with your first fork. The essential problem is developing your eye for where the bend is, so that you can apply your re-bending force there, rather than just "pushing at what sticks out."

The method(s) you use to apply the appropriate force will depend on the tools at hand. It must be remembered that for the "creative fixer" tools don't often look like tools, so some imagination is necessary. Suggestons previously made are pretty good, but are only a partial list.

After you have made your best attempts, quite likely this fork should be set aside as the "loaner" you keep for the neighbor who never brings things back. Once he/she loses it, you can apply your persuasive powers to shaming said neighbor into buying you a replacement. Since such "borrowers" invariably will - even in the rare instance when replacement actually is made - come up with the shoddiest imitation possible, you should in the mean time get yourself a good replacement for your own use.

When you get your good quality replacement, you should refrain from trying to pry tree roots, rocks, and water pipes out of the ground with it. For these, you need a different tool. There are specialty tools designed for the purpose, but I use a 5-foot long x 1.5 inch diameter axle out of a Massey-Ferguson combine, hammered to a point on one end.

John