If your family resides in the United States, contact the local public school district for your residence to learn more about their kindergarten enrollment policies and procedures. The dates for kindergarten enrollment vary. You can research the contact information for local school districts and schools in your area via SchoolFinder: http://www.education.com/schoolfinder/
You'll get the best search results in SchoolFinder by entering your city, state and zip code.
I'm also including some additional resources below that you may find helpful.