The username and password used to login to the router settings page aren’t the same as the wireless name and password used to connect via wifi. If ‘admin’ isn’t working, take a look at the manufacturer’s website and look for a setup guide. As for the password, it may be blank by default, or it could be ‘admin’. It will vary depending on the router model and manufacturer. In most cases, it’s easy to find via Google.
If you’ve previously changed the password or user name and you’ve forgotten the login credentials, many models will have a Hardware Reset Button located on the router itself. This can be used to reset the router back to factory settings.