Open the deal where you would like to add a document or photo from your mobile phone.
Tap on the "Documents" icon to open the documents view.
Once there, by tapping on the orange "+" icon you will have the options to add a document or photo from your phone.
If you choose to add a photo, you will have the additional options to take one with your phone camera or to choose and existing one from your gallery.
The maximum supported file size for documents and photos is 25MB and one document/photo per upload.