You have to go into editing your service, then you'll see the buttons in a pane to the right, and a browser tree to the left.

On the left, browse to the location that Butterfly valves are stored, and you drag and drop it into the right pane and now you have a button for it.

Make sure to do due diligence however once it's in your service. ie: Set if for a Flanged, set upper and lower limits, whatever you need to do to make it match your service.

Alternately, you can also download content by going to that service way back at the beginning, before you step into any of the "edit" locations, right-click on an empty space, and click "Download content to Here"... there's all kinds of content available. 

You may get more than you wanted. If that's the case, go into edit your service, and delete whatever buttons you don't want.