Most magazines get into stores through their distributor, who contacts stores on behalf of the publisher to determine the draw (how many copies the stores will stock), to analyze the sell-through and to physically ship the magazines. In some cases, retailers might work directly with a publisher to stock their magazine, but this is rare.
Some distributors insist on being the sole distributor while others will work with a publisher who has another distributor. Having more than one distributor can lead to confusion, including double shipments to the same retailer and figuring out which portion of the payment goes to which distributor.
Promotion to libraries is difficult unless your magazine is carried by EBSCO or CANEBSCO, the subscription services used almost exclusively by librarians. Magazines Canada regularly markets it member magazine to libraries and sends librarians its Retailer Catalogue, as do some of the regional associations in Canada.