I've just upgraded TFS from 2012 to 2015. If I create a 'Feature' can I move PBIs under it so I can organise all of the PBIs into 'Features' and 'Epics'?
To map a backlog item under a feature:
Then you will see the dragged PBI under the corresponding feature.
More detail info please refer this tutorial: Map items to group them under a feature or epic