Is it possible to implement Yammer in sharepoint 2013 on premise?
What's the prerequisites needed to do that?
Using Yammer with SharePoint on premises is a completely different and more complex conversation.
You will need to configure access to the SharePoint Store to download the Yammer App. Microsoft created the SharePoint Store to move away from using managed code in the SharePoint environment.
You will need to add a DNS address to enable the connection between your SharePoint environment and the Store.
You won’t be able to install the Yammer App without this configuration so make sure you work with your IT group to ensure your Server environment is set up properly before moving forward.
More information from below articles:
Yes, you can integrate Yammer with on-prem SharePoint 2013. Here are the docs from microsoft on how to set it up. To be clear, there is no on-prem version of Yammer, so the end result of following this procedure are things such as providing a link to yammer in the nav, and replacing the newsfeed with a Yammer feed.