We are using GOOGLE FORMS for registration purposes.
If you have GOOGLE account, You can easily upload your abstract (and later the full paper) using registration form. You can do it immediately upon registration, or later using the link EDIT RESPONSE in your registration confirmation email.
If You don’t have the GOOGLE account or you don’t want to register using existing GOOGLE account, you can still register using the form without upload options. You can additionally email your contribution to the conference vice chair.