how to perform auto-login to a webApp

I need to perform an auto-login from web app A to B.

B uses OpenID Connect to handle authentication.

I call "oauth/authorize" endpoint to redirect me to allow access :

example: https://websiteB.com/api/oauth/authorize?response_type=code&client_id=123456&scope=test&redirect_uri=https://websiteB.com&state=xyz

but it shows me this error

does i need to get the Site B redirect url?

wich part of oauth flow should i use to rdirect the user to site B?

I had never used OpenID, so it will be a great help if someone guide me in.

thanks in advince.