how to patent an idea?

You need to understand that an "idea" must be implemented as a "new and non-obvious" invention in order to even file for a patent. It's not that easy to properly disclose and "claim" an invention, which is why good patent attorneys are well paid.

Try your basic research at uspto.gov/patents FAQ and some wikipedia summary articles:
en.wikipedia.org/wiki/Patent_application

You send a letter to a patents office detailing what you want to patent.

Call George Foreman.

from think