I am new to the forum and to flashing routers. Although I have managed to connect to the hidden serial port of the router using the instructions from https://openwrt.org/toh/sky/sr102
But it is absolutely not clear to me that how do I download a new firmware onto the router. Could someone please provide me a clearer explanation.
The page you linked is the best resource. It does depend on some third party builds to get the CFE. Replacing the CFE has a considerable risk of making a "hard brick" that doesn't even boot to the bootloader. Overall it doesn't look simple at all.
Also note that there are no drivers available for the WiFi and DSL functions, so it would be usable only as a wired router (though with GbE and dual core CPU it would be a fairly powerful one).
I used lighttpd mini web server (linux) and put burn_whole_image and openwrt-brcm63xx-generic-SKY-SR102-squashfs-cfe-with-luc.bini in / var / www / html /
So in the router in / var directory
wget http: // ip-computer / burn_whole_image
wget http: // ip-computer / openwrt-brcm63xx-generic-SKY-SR102-squashfs-cfe-with-luci.bin