Post an update and attach files
Start a conversation in Yammer to share information and updates across your organization.
Post an update
Select Update and type a message.
@mention people who'll find the post helpful or interesting. Or, use a hashtag on topics relevant to the message so others discover it.
Upload videos, photos, and documents to your post for context and collaboration. Or, add a GIF to help emphasize your message.
Attach files to your update
Select where you'd like add a file from: your computer, SharePoint, or Yammer.
Go to your file, select it, and then select Open.
Select Post to share the update.
Source: Microsoft