Following the earlier announcement, Microsoft has started to upgrade existing Office 365 E plan to allow them to get Enterprise Yammer.
You have to start the Yammer upgrade from your Office 365 Portal.
Log on to your Office 365 administration portal with an administrator account; if your tenant is ready for the upgrade, you should see a new section below Service Overview called Included Services
Click on this link and then you will be able to click on the Yammer Enterprise Activation link – Yes, activate Yammer Enterprise for my network
Then you will be asked which domain has to be used for SSO – you can associated new domain from there too
NOTE If you don’t have any associated Internet domain, you will be asked for associate one
The activation process is in progress; it may take some time to complete
Starting then, Yammer is now displayed in the Dashboard
Once the provisioning is finished, Yammer is now appearing in the Admin menu, and the Included service link disappears from the Dashboard
You can now manage your Yammer Enterprise… 
First thing, there is no need to associate a Yammer license to a user account as shown below
So, if you hit the Yammer link from the admin menu, you will be redirected to the Yammer portal using your Internet email address
By default, the Yammer administrator is set to the user account which starts the Yammer upgrade
With the Yammer administrative rights, you will be able to manage your Yammer network
Add additional administrator
The first thing is to add (maybe) additional administrator; to do so, just hit the Admins menu on the left side
Just enter the additional administrator name; the system will automatically propose name(s)
After selecting the user name, check the Make this user an admin option
Once the user added as administrator, click on the Grant verified admin button which appears on the right side of the added user
You can later decide to revoke or remove this user as administrator, so just go to the same Admins menu and click one of the button Revoke Verified Admin (temporarily revoke administrator rights) or Remove (definitively remove the user from the admin list – you will be able to re add him again if you want)
Configure your network
Hitting the Configuration link on the left side allows you to manage your network – change the name, enable/disable features
Changing the network name doesn’t change the URL neither the email address @yammer.com associated with
Design
The design link allows you to change the style sheet used for your network as well as adding your company logo
Directory Integration
To ensure all your user is automatically added to your Yammer network – allowing to disable the Yammer registration process, just go to the Directory Integration menu below the Users section on the left. This requires before the Yammer directory synchronization tool to be installed and configured – see http://blog.hametbenoit.info/2013/12/02/yammer-synchronize-your-directory-with-yammer/
