Determine which right hand lever extensions you need, match the levers on your harp to the pictures below. Then you can pick the right extensions. Next to each picture of the lever is a list of the Extension that you will need.

For the Brass tube with screw lever extension click here.
For the "O" ring extension click here.

Once you get your lever extensions, you will want to experiment to determine the upward angle needed to engage the lever. Try to avoid rubbing the string on the tuning pins:
Here's how the two different extensions look on the lever: