Apple Care Expiry and Renewl

Hi,

I got a phone last March and wanted to add apple care before the expiry of the 1yr manufacturer's warranty! it's in perfect condition I didn't know there was apple care even as an option since I got it at best buy...

I also had a Macbook air that has its AppleCare expiring in less than a year how could I go abt renewing it??

Thank you in advance!!