You will need the Read Document Library permission to open the library, and Write Document Library to upload, rearrange or delete files and folders. Which organizations' libraries you see depends on your campus access, not on the permission.
The Document Library opens from the Files folder icon on the top toolbar.
Using the library
In the Document Library you can upload documents and organize them into folders. Those documents can then be opened when you need them, included in an outgoing email, or added to a record such as an event description or mobile app content.
Download a file by double-clicking it, or by right-clicking it and using the menu that appears.
Turn on the eye button
in the upper right to show a preview of the selected file in the right panel, where available, along with details such as its link, who uploaded it and its size.
The leftmost panel shows every folder. Drag and drop files into folders as needed.
Every file has its own URL. Right-click the file and choose Copy URL. The URL never changes, so you can move a file to another folder without breaking links to it in emails or on your website.
Read and write access
Read Document Library - read-only access. You cannot upload, rearrange or delete files and folders.
Write Document Library - full access. You can add new files, delete content, and rearrange files and folders.
Each is one permission per person. If you can reach an organization, its whole library is open to you. There is no per-folder or per-organization access.
Libraries and organizations
Every folder and file in the library belongs to one organization. If your account has one organization, that is your default organization.
A folder and all of its files stay in one organization, so a folder cannot mix organizations.
Someone with no campus or organization limit sees every organization's library.
A limited person sees the libraries of the organizations their campuses belong to. Opening a library outside their reach shows Organization not found.
What is an organization? explains how organizations relate to campuses.
Storage quota
The lower left corner of the Document Library shows the storage in use. It uses the same storage quota as your subscription, so the bar includes not only the Document Library but also sermon audio and video files and files in the song catalog.
The maximum file size in the Document Library is 50 MB.
Storage limits by organization
If your account has two or more organizations, each organization can have its own storage limit. An upload to the library is checked against that organization's limit, if it has one, and against the subscription total. The subscription total always wins.
When the organization's limit stops an upload, the message names the organization, says how much room it has left, and points you to Account Settings > Organizations to raise or remove its limit.
When the subscription stops an upload, the message says how much media storage is left and suggests upgrading your subscription.
When an organization is archived
Archiving an organization moves its document library under a new top-level folder in the organization you choose. How do I archive an organization? explains the rest of the archive.
Warning: If the moved library would take that organization past its storage limit, the archive window warns you, but the archive still goes ahead. Uploads to that organization are then refused until it has room, so raise its limit or delete files.