To log in on the PC version of the QQ application, you first have to register your email address in the application. There is a section that allows you to attach an email address to an already created account. After you have added and configured the email, you can install the PC version of the QQ IM and log-in and that's it. After you log-in, add the photo you want to your profile. This is how these applications works (eg. WhatsApp, Line, Viber, etc.)