The files you upload to a project are stored in the project's document room inside document groups. Document groups are separated into primary files and secondary files. The priimary file will always have the most recent version of that file at the top, while secondary files can be any file type.

You have the option to connect a document group to the schedule and to give that document group a due date. If you choose not to give the document group a due date, then you can still share that document group with your team including guests, but that document group will not be tracked or managed in the schedule.

If a document group is given a due date, then it will automatically be connected to the schedule. Then when you share that document group with your team, they will be assigned to the due date for that document group.

You also have the option to upload and store files in the document room without connecting them to the schedule, and to share these files without a due date.

First you'll need to upload your primary and secondary (supporting) files to the document group inside the document room. You access the document room by clicking on the project card from the dashboard:

If you've created a project from a template then the document room and schedule will be automatically populated with best practice items, including document groups, actions and tasks. These items will be added both to the schedule and to the document room. Assign a start date and due date to the document group, and then select the + sign to assign your team members. 

If progress has already been made on the document, you can represent this on the schedule by adding a value to the completion percentage indicator, and/or you can ask your assigned team mates to do this from the schedule by clicking and dragging the progress metre.