When I connect to wifi, I get a "weak security" message. How do I set up WPA2/WPA3

Change the security settings on your router to WPA3 or to WPA2 AES. How you do that varies by router. If you don't have the instructions for your router, do an internet search for instructions for your router brand/model or if your router is supplied by your internet service provider, check their website or customer support. Also see: Recommended settings for Wi-Fi routers and access points - Apple Support