I recently answered a question on how to enable a custom entity for activity posts or yammer. Here is the answer;
In my solution I have Yammer enabled which effectively replaces the out of the box activity wall posts. But with or without Yammer the process to enable a custom entity for posts is identical. The steps are below;
First of all, for my test I needed a custom entity. (You will probably have an existing one you wish to enable!) Being a quick test mine was really simple. The only thing to be sure of is that the entity will need to be enabled for activities. As the Yammer feed will show in the social pane which is only present when you have activities.
Tip: Ensure you have done a publish all BEFORE you start this process!
Next you will need to find the activity feeds configuration option in settings.
Now when you first look for your custom entity in this list it is quite likely to be missing! So select the refresh button from the ribbon. After a short pause you should now be able to scroll thru you list to find your entity.
As I scroll down I can now find my entity but you can see the status is set to inactive. Simply select the row and select the “Activate” option.
At the next prompt select “Activate”.
There will now be a short pause whilst the activation happens. Followed by a message something like this;
So next you need to publish all customizations. As directed!
After your familiar yellow box disappears you can view you entity. See below that the social pane on my custom entity now includes Yammer and System posts.
I hope this post has answered the question asked and is helpful. J