You must be logged into your account on CitySquared.  In the top left corner, click Dashboard

Find the registration in question.  Click on the application to open it and at the bottom of that screen you will see a Documents section. 

This is where all documents for your registration are stored including your Certificate.  To view any of the documents, just double click to open To upload documents, click the Edit button next to it.

Click to upload or drag and drop the documents you need to include with your application and click Update.