You are able to add a Photo Field into a Form Template via the Web Portal by going to Forms > Existing Templates > Select the Edit Arrow for the Form Template > Form Builder > Drag and Drop the Camera Icon From the Toolbox - Advanced section to where you would like it to go in the form > You can enter a question or title of the photo field on the right hand side in the Field Settings.
Be sure to Save Draft and Deploy / Publish Template to save the changes that you have made to the template, to use in future new forms created with it..
