How do I upgrade to Android lolipop

I have a 32 gig sd card but cannot utilize it because there is no option to store apps on it my tablet has an internal storage & a built in usb storage & there is an option to movie apps from one to the other but not to the sd card, I downloaded ASTRO file manager so I could move my apps to the sd card but when I tried it said I have to uprgade to android lolipop to be able to do that, so I would like to know how to go about doing so.