How do I rename our WiFi using a Mac?

You do that by logging into the router. How you do that will depend upon the instructions for doing that in the router manual. Normally there is a special IP address you enter into a web browser and then you need the router password which may be located on the base of the router itself.

Read the router manual.

Use IP Scanner Home app to sign in to the router., see https://apps.apple.com/nl/app/ip-scanner/id404167149?mt=12

Tthen you can change the Wi-Fi network name, see this Apple article: Recommended settings for Wi-Fi routers and access points

https://support.apple.com/en-us/HT202068

Thanks for your feedback & you're welcome.