There is a community built Leap driver which allows you to use our hand tracking within SteamVR by emulating VR controllers. We do not have any official or Ultraleap built drivers to connect our hand tracking with SteamVR and the Leap Driver by SDraw has proved to be a good choice for many to connect our hand tracking to this platform.
Please see this forum post here for more details on this and a link to download the driver itself.
This should help you to get up and running with hand tracking in SteamVR. Please let me know how you get on with this.