There are two broad paths to register for Amazon Easy Ship once you are a registered seller on Amazon.
You will be enrolled in the program, and henceforth all your eligible orders will be delivered through Amazon Easy Ship. You will have to schedule the package pickups within Seller Central and prepare the package for the delivery associate before the allotted pickup window begins. See Managing Amazon Easy Ship Orders help page for more information. You will not be allowed to sell or ship products that are restricted from the Amazon Easy Ship program.
Follow the link at the bottom of this page for more specific steps on another way to check your eligibility and register for Amazon Easy Ship.