Basic steps:

1. add a popup window under Window list, set properties for it in the properties panel of popup window.

2. add components to popup window, set properties and actions for the added components.

3. add a hotspot to the scene or add a button to main window.

4. add an action Window> Open Popup Window or Show/Hide Popup Window from the Actions panel to the hotspot or the added button.

5. click OK. Then preview, when you mouse click on the hotspot or button, the popup window will appear as you have set.

See a sample tour at Gallery.