We update the server list the same way we installed it the first time. Use wget to copy the server settings specific to your account.
root@OpenWrt:/etc/config# wget https://blockthis.xyz/api/luci-xray/UseYourOwnUrlNotThisOne -O /etc/config/xray
Downloading 'https://blockthis.xyz/api/luci-xray/UseYourOwnUrlNotThisOne'
Connecting to 123.123.123.123:443
Writing to '/etc/config/xray'
Download completed (72220 bytes)
root@OpenWrt:/etc/config#
Then (re)load the Services > XRay page in the web interface to see the updated servers.