Now before you try treating your own broken bone, I would always recommend seeing a medical professional if available. However, if SHTF and you need to get your broken bone treated, this article will be a good source of information.
I recommend reading this article in entirety because it was written by a medical profession. More importantly, it was written by a prepping doctor. Enjoy the read and bookmark the article if case you ever need it.
How to Set a Broken Bone or Treat a Dislocated Joint