You go in and ask the library director at your local library to add it to the collection, armed with a batch good reviews, preferably from journals like Kirkus and Publishers Weekly. Most libraries will only add books that have been published by non-subsidy presses and reviewed by one of those journals. That being said, most libraries have some capacity to order books by local authors. My advice would be to offer to donate the book to your local library if they're willing to add it to their collection. (Most donated books end up on the library sale table -- so definitely check.)