Mastery Chests

I have a few questions concerning mastery chests. I have several champs that the client shows that I have earned a mastery chest for. How do I claim those or will they just be passed out automatically? Secondly, will the chests need a key to open or will they not require a key to open? Some people probably forgot about those or just don't care but I have somewhere around 20 or so chests that I should be getting through the system.