Backup your files and database first. You can backup your database by going to Opencart > System > Maintenance > Backup/Restore, selecting all and pressing the Export button. This will also include all Journal settings such as modules, styles, skin options, etc.
Update the Opencart system. Do not update to an unsupported Opencart version. The supported Opencart versions can be seen on the General Info page of this documentation.
Upload the latest theme version on top of the new Opencart update immediately after you've updated the platform. DO NOT access your admin before you upload Journal again as Opencart may reset your theme settings.