Updating WLED can be completed a few different ways:
Upgrading via USB (serial) connection requires a full re-flash of your WLED board. This will erase all existing configuration.
If you choose to use this method, make sure to backup all Config and Presets prior to re-flashing so all configuration can be restored after the upgrade.
Just follow the WLED installation instructions will the additional step of taking backups.
To upgrade over the network, download the correct .bin firmware file for you board and upload it to your board to be used as the upgrade source.
NOTE: There is a known issue when updating boards from v14 due to legacy partition sizing preventing the new FW from installing - insufficient space. To upgrade, you must re-flash the controller with WLED. This will erase all configuration - make sure to download Config and Preset backups.
On a correctly partitioned WLED installation, the Filesystem metric should read a total of 983 kB.