How do I change the settings on my router?

The details of how to change router settings varies by router. Do an internet search for instructions for your router brand and model.

Are you looking for the recommended settings - or for instructions that relate you your own WiFi Router. Assuming that you are looking for the former:

Recommended settings for Wi-Fi routers and access points - Apple Support

Your WiFi Router is most likely managed from a web-page. You will need to find instructions or guidance from the manufacturer of your Router - although if the router was provided by your Internet Service Provider (and many are), you will need to look at your ISP’s tech support pages.