Block website using snort3 in openwrt

i want to block a specific website on the openwrt router using snort3 , how can i achieve this

What's wrong with the pre installed firewall?

Yeah, you're much better off using both the firewall and a dnsmasq-based block lists than snort3 for blocking website access. Snort3 is a real pig (hence its name), it requires a pretty big box just to start up (1GB+ free RAM, x86 or Pi4-sized ARM CPU) and is huge overkill for what you're asking.

If you are intent on using snort3, read up on rule writing. Probably start here, maybe this one, too