Update from 5.5.5 to 5.5.31 or later?

Hi All; I'm trying to install Moodle and get it working, and it's reporting that my server is running mysql (5.5.5-10.1.30-MariaDB) and that is requires at least 5.5.31 I have not been able to figure out how to get the update onto my server; I thought it was supposed to do it automatically, but so far it hasn't. All my Google-Fu has not turned up the answer so I hope someone here can point me in the right direction. Thanks Heaps, Mathew.