Adding newsfeed to an upgraded SharePoint Team Site
Found a great little post about how team sites look before and after an upgrade from SharePoint 2010 to SharePoint 2013.
In the article, it mentions how to turn on the newsfeed (something that is included with NEW SharePoint 2013 team sites). I had already figured out that the newsfeed was a feature called "Site Feed" and had activated the feature on my upgraded team site, but I was having trouble finding the web part to show the newsfeed – it just wasn’t in my web part catalog.
Turns out, that my team site is a subsite, so I activated the "Site Feed" feature on my site collection and the web part then became available in the catalog of my team site.