Yammer Enterprise has been released as a part of Office 365 Enterprise Plans. Now how do you activate it and more specific how you connect it to your already existing network(s).
First thing first activation:
When you enter your Office 365 dashboard you should see this when your tenant is ready for Yammer:
You can click on the Yes, activate Yammer Enterprise for my network.
When you already have a Yammer version connected your domain or you need to create one, that’s the easiest way and according to documentation also the recommended way.
When you want to upgrade multiple networks; e.g. when your users don’t share a common email address or work in disparate business units or unrelated subsidiaries, then you need to upgrade a primary network first, and contact Yammer Enterprise Support to upgrade additional networks
When upgrading and merging domains; e.g. an organization that has multiple business units or subsidiaries that want to take advantage of the collaboration and administrative features of Yammer Enterprise but don’t share a common email domain; we recommend that you choose the most relevant existing network, that is, the network with the most content or users to be your parent network. You’ll want to consider this option carefully because merging email domains will cause users to lose access to any content that was created in their original Yammer network. you might want to contact Yammer Enterprise Support to work through the plan for a network merge.