The Mobile App users, depending on the access rights granted to them, will be able to upload documents/files inside the projects.
In order to upload data, you must first position yourself in the location you wish to upload the data to.
For example, if John Smith is working on the Satterfield Corners House Project and he wishes to upload photos of the works under the Client Files folder (that can be made visible to the client), he will have to open that specific project > Go to Files > click on the Client Files folder > click on the red "+" button in the bottom right-hand corner and choose from the 2 options: Upload files or Add directory (add a folder).