If you have 3.2-t, or a version from me anyway, and want 3.3.-t, it is enough to enter in fastboot, or fastbootD mode for Samsung, and then:
$ fastboot flash system new-gsi-system.img
$ fastboot reboot
If you want an upgrade, use Updater from Trebledroid Settings. Consider the possibility of an update failure, so make a preventive backup.
The indication is generic; take into account the particularity of your device.