This first step is to identify the school district for your home. SchoolFinder can help with that:
 
http://www.education.com/schoolfinder/
 
Enter your city, state and zip code into the search field for a listing of schools and the school district (the link to the district info is located right under the search results map).
 
Next, contact the school district and find out from them which elementary school your home is zoned for, and what their district and school age requirements are for starting kindergarten.
 
Once you have the name of your child's designated elementary school, contact that school to find out their registration process, paperwork and deadlines for kindergarten enrollment. If the district didn't give you the school's phone number or other contact info, return to SchoolFinder to get it.
 
I'm also including below some additional kindergarten readiness info you may find helpful. Congratulations on this special milestone for your family, and especially for your young student!