here is the release notes you can jump directly to 12.X
https://www.cisco.com/c/dam/en/us/td/docs/security/security_management/sma/sma12-5/SMA_12-5_Release_Notes.pdf
you can upgrade from GUI
system Administration -> system upgrade
Click Upgrade Option
it wil show you under "List of available upgrade images files at upgrade server: "
select the version and proceed follow the process.
until the upgrae success, the new version will not take effective.
Notes :
1. backup the config ( with out masking the password)
2. download the config out of the box
3. read the realse notes and caveats.
4. upgrade in maintenacne window, it required reboot.