After completing all sections of the online application, you will need to submit information (name, email, title, etc.) regarding your references.
Most graduate programs require three letters of reference. Check with your proposed program of study office regarding the number required. Your recommenders will be required to submit letters of reference using the online recommendation system.
The application will require this information prior to allowing you to submit your online application. However, you do not need to wait for your recommenders to submit their letters before you submit your online application. You can and should submit your online application prior to your recommenders submitting their letters.