Can you teach me how to add a wallet or show me how to do it as an example?  

I get the message 'connect string isn't valid' all the time, maybe I still don't get it. 

 Go to nwc.getalby.com and create a nostr+walletconnect:... string there? 

 I put something like this, is it correct? (still not valid)

https://image.nostr.build/2e76a6ccc5589d2e86d3b5a37232532accaf4106a125d30508a025db38d652c4.jpg 

 Something like this but it's not a correct link, where did you get it? 

 Remove pubkey= then it might work