https://xenforo.com/help/twitter-integration/The website and callback URL should both be set to the Board URL value set in XenForo. It's very important that the correct domain is entered here. Registration will only work if the request comes from the domain entered here.
When I test the integration it gives me this error:In that case, if what's in ACP > Options > Basic Board Information > Board URL matches exactly what you have entered as the callback URL in https://apps.twitter.com then it should work.
If you say it doesn't work, you will need to give some more details than that. Why doesn't it work? What is (or isn't happening)? It's a bit difficult to troubleshoot without further information.