To the right of each meeting or event, there is a drop down menu with the option to Add Documents to your meeting. This feature allows you to provide supplementary documents to your meeting attendees that they can check out before or during your meeting. You could also add your meeting agenda so that folks can get a sense of what to expect and what will be discussed.
First, you'll need to have setup your meeting or event.
Article: How to create a new meeting or event
Then head to the Meetings & Offline tab, find your meeting, and click the dropdown menu (⋯) on the right side.
Select Add Documents from the dropdown menu.
The Add Documents window will pop up. Drag & drop or choose the file from your computer to add any supplementary document(s) you'd like to share with your attendees.
If you've made the meeting public (default) on your project group or page, your document(s) will appear just under your meeting's info:
How to set up a meeting or event