-
Sign in to your hub via the web interface, it's possibly http://192.168.1.1 or something like that.
On the bottom left there is an "Administration" category, and within that a tab for "Firmware Upgrade".
You need to extract the .zip you downloaded locally, and using the form on the Firmware Upgrade page pick the .trx file you extracted and upload it.
Once it has flashed, it will require you to reboot it. When it comes back up, the interface will be slightly different (more recent)... then you configure however you like.
In future Administration > Restore/Save/Upload Settings will mean that you don't have to config anything again.
Ok, downloaded https://www.mediafire.com/folder/bkfq2a6aebq68/Asuswrt-Merlin#2324w3jh7e4q4.
Installation (https://github.com/RMerl/asuswrt-merlin/wiki/Installation) says "Just flash it the same way you would flash any regular Asus firmware." except I have no idea how to flash regular Asus firmware. Does it have a USB slot or something?