How can you heal a broken wrist?

Immobilize. This is a strange question. Are you sure that it is broken? Fractures involving the wrist can be complicated and lead to permanent pain and disability so it is imperative that you seek proper evaluation and treatment. In other words, go see your family doctor or a hand specialist without delay!
Splint it. Imobilize for 6 weeks to allow bone to heal. Failures in bone healing are related to motion at the fracture site or poor blood supply or a combination of both of these.