Updating openwrt firmware on Mini Router

I’m using Mini Router - mostly all good - I’d like to update the firmware. It is a bit daunting. Can I use the built-in “sysupgrade” mechanism? Do i have to re-flash the box using the same procedure I used at the beginning. This would presumably lose all my settings.

Please could you let me know the recommended upgrade process for this device. Thank you!

I’ve asked in a few places with silence … now trying here too.