You build forms and everything they need to function through one of the BlinkMobile Platform's tools, called the BlinkForms Builder. It is found under the 'BlinkForms' option on the left hand menu in the Interaction Manager.
Once you've chosen this option, you will be presented with a list of forms if they already exist. Click the 'Add' link at the bottom left of the listing and the following (or similar) screen will appear: