Warranty on items bought online?

I just bought a Michael Kors watch off a reputable ebay store. It is genuine btw I have another watch and its definitely real.... Michael Kors watches come with 2 year warranty so I'm juat wondering IF something was to happen to my watch what procedure do I follow? Do I send it back to the ebay store? Straight back to MK? Should my booklet have the company stamp in it or something showing my date of purchase? I obviously have a paypal page of my order details, is this sufficient? I'm generally very good with my things, very careful so this is just a what if situation. Any help appreciated :D