1. Select the button that you want to add an action to.
2. Click the Add Action/Behaviour bar in the button's settings panel.
3. Select a type of action or behaviour (In this example we will use the fade out action)
4. Choose a target element for the action (in this case we will use an image but you can select just about any element type including the button itself), and then click apply.
5. Edit the action properties as desired and select trigger (In this case we will use the Mouse Down trigger, where the action is triggered as long as the mouse button is help down over the button) and click OK when done. Your button now has an action attached to it, you can now preview the site and text it to make sure it has the desired effect.