How do I change SSID on my router

You need the user manual of your specific modem-router model (I think you can download the manual opening its manufacturer's website and searching for support).

When done, these are the suggested configuration options you should look for:--> Recommended settings for Wi-Fi routers and access points - Apple Support

Regards

Giulio

It depends on your router. In general the procedure is:

• Use a desktop connected via Ethernet (best option) since if you chnage the name a Wifi device may disconnect
• Open a browser (such as Safari) and connect to router: checked your documentation for router address. It shuold be something like 192.168.0.1
• Enter router configuration mode and follow router instructions
• You might have to restart router afterwards

That's the general procedure...

Maurizio