You can login to QQ International by using the email address provided when you signed up for a QQ account. This email address and the corresponding QQ number/ID are equally valid forms of identification.
Because your email is linked to your QQ number you have the option to use email as your screen name (please refer to this article for further details).
How do you change the email address associated to your QQ account?
When QQ International for Windows is running you must first open the Main Panel then click on your personal picture to open up your Profile, then click on the little icon next to your name.
Please notice that this action will open a website in Chinese where you can easily change your credentials. Check this out if you need help understanding our pages in Mandarin.