The following is general procedure; specific commands for Linux may be found here.
Before you update to a new version of FreshRSS, it's always a good idea to backup your current installation. Simply make an archive of your FreshRSS directory, which can be restored if needed by following the "Updating from a Zip Archive" section at the bottom of this document.
If you enabled web updates from your installation (see footnote 2 in installation), you can log into your admin account, select the update option under Administration in the Settings dropdown found on the top right of the webpage, and press the "Check for new updates" button. Alternatively, this page can be reached directly at http://<your_server>/i/?c=update.
This will check for and apply a new Stable version, if available.
If you installed FreshRSS using git, you can update, change branches, or switch to a specific version from the command line.
Generally, the update procedure via git works as follows:
./data/do-install.txt.., and group write permissions on ./data/.Updating to a new version from a zip archive is always an option. Begin by unzipping the archive into your FreshRSS directory, overwriting old files, remove ./data/do-install.txt, and finally re-set group read (and write, if you wish) permissions on all files in . and group write permissions on ./data/.