Wizidge As ntozier said, there are no database changes from 1.12 to 1.12.3, so simply uploading the files downloaded from the osTicket website is enough. There are no additional upgrade steps to be run. You can confirm the new version by going to Admin -> Dashboard -> Information where you should now see it listed as 1.12.3
EDIT: note that the download was updated recently due to the version incorrectly displaying as 1.12-git. If you're using one you downloaded a few days ago, try downloading again. See https://github.com/osTicket/osTicket/issues/5084 for details