Logging in from google to logging in from websites

I had logged in from Google on "udemy" and subscribed for some paid course, all that is working fine but now if I have to log in from the "udemy" itself and use the already paid content how can I do so? I do not want to log in from my google account but simply from the website, If I sign up there for a new account then I could not able to access the purchased course which I want to access, what could be the steps to make my job done.

thanks.