I forgot name and password of localhost episerver login. from where it can retrieve ?
If you are on latest version of Episerver, you most likely have Identity-based authentication, right?
If so, you might be able to see the username in the DB using SELECT * FROM AspNetUsers. However, unless you've saved it in the browser, you'll have hard time with the password.
So, it's probably better to create a new user, check this post out and Dejan's answer.