In order to Upload a Document from your internal files:
Go to Content Builder > Select an e-Folder or Create a New e-Folder
Select a course
Ensure Maintenance Mode is enabled to prevent user access whilst you're editing it.
Click Save
Select the Documents Section
Click on the Plus icon to upload a new Document
Type a Title for your Document
Add a Description
Drag and Drop your document or select Browse file to locate your Document
Enable Add to Library if you wish
Add Tags so you can easily locate your document
Make the Document Mandatory if you wish
Click on Save to Upload your document
Click on the 6 dots to drag the document from your Document Section to the Course Content