To add a link to a button, click on the button. When you have selected the button, you will see a “Link” field in the left upper side of the editor where you can type the link URL.

This is how you can do it in the Chamaileon editor:

It is also possible to add a title to a button:

If you are not using Chamaileon yet, you can register here for free and add a link to a button easily.