Before changing anything at your FlatPress instance, always create a full backup of the whole FlatPress folder (how to).
If anything goes wrong during the update process, you can simply delete the complete blog and copy it back from your backup.

To see your current FlatPress version, go to Admin Area → Maintain → Check for updates.

Testing the lastest version? The following steps work exactly the same for the Release Candidates of FlatPress 1.5 "Stringendo".

• At first: Create a backup of your blog. This enables you to rollback your changes in case of errors.
• Unzip the update package 14to141.zip and transfer its contents to your server. Overwrite existing files.
• Rebuild index and caches: Admin Area → Maintain → Rebuild index and Purge theme and templates cache

After updating as described, the FlatPress backend (Maintain → Check for updates) displays “You have FlatPress version 1.4.1”.

To update from FlatPress 1.3 (or 1.3.1) to 1.4, please use the update package 13to141.zip.

Since FlatPress changes its way to store your authentication from 1.3 to 1.4, updating is not just copying files this time.
⚠️ You'll also have to re-run the setup.

• At first: Create a full backup of your blog.
  Don't skip that step, you'll need data from that backup in step 6.
  Also, this enables you to rollback your changes in case of errors.
• Unzip the update package and transfer its contents to your server. Overwrite existing files.
• Delete fp-content/%%setup.lock on your server.
• Run the FlatPress setup by pointing to yourblog.com/setup.php.
  When asked for the admin user during setup, enter the user name, password, and email of your current admin user.
• When the setup is done, log in with your admin user.
• The setup set your configuration to default values (see the blog title, the theme etc.). Restore your config by copying the fp-content/config/ folder from your backup to the server. Overwrite existing files.
• Your browser needs to load the new JavaScript: Delete your browser cache or hard-refresh your blog (Ctrl + F5).
• The setup created a new "Welcome" entry. You may simply delete it.
• The update package overwrote the Favicons. Restore your custom Favicon (if you had one) from your backup to fp-plugins/favicon/imgs.
• Finally, rebuild the index and the caches: Admin Area → Maintain → Rebuild index and Purge theme and templates cache

After updating as described, the FlatPress backend (Maintain → Check for updates) displays "You have FlatPress version 1.4.1".

For older versions, please follow the update instructions of the release you wish to upgrade to.