If you need to create a new file in Word, PowerPoint, or Excel, you can add one right in Yammer.
Create a file
From your Yammer home page:
Select Create a File.
Select the drop-down arrow and select the file type you want.
Type in a file name, and select Create.
The new file opens in another tab, and also appears in a Files list that all group members can access.
Edit a file
From the Files list in your Yammer group:
Select the file you'd like to modify.
Select Edit File.