If you are struggling to find where to add capabilities for adding Ant builds to your build server I have the directions.
Browse to the URL -> http://<yourserver>:8080/tfs/_admin/_AgentPool
Click the agent you would like to add the capabilities to and click the “Capabilities” link. It’s sort of non-obvious as it is just a gray word next to the “Requests” link which is selected by default.
Once you’ve selected it in the USER CAPABILITIES section click the “Add Capability” button. A new empty row appears. Enter ant in the first text box and yes in the right text box.
Restart your build agent from the TFS Admin Console on your TFS build server.
Queue a new build and you should be all set.