Transmitting on GMRS frequencies requires a license from the FCC, however no knowledge test is required to obtain a license.
A license covers you and your immediate family members and is valid for 10 years.
Right now, the fee is $35 for the 10-year term, or only $3.50 per year.
The list of GMRS and FRS radio frequencies and their restrictions.
You must follow the rules under Part 95 of Title 47, Chapter 1, Subchapter D under the Code of Federal Regulations.
This subchapter is broken into many subparts. Subpart A regards the Personal Radio Services generally and Subpart E regards GMRS exclusively.