Many a times, you would want to display a popup when a user clicks on a Menu element. You can do this using the Modal popup module that comes with the PRO Modules
Here are a few steps you need to follow:
1. Create a new row template by adding modal popup inside it.
2. In Display Settings of Modal Popup, select Custom Class / ID option & enter the unique class name there.
3. Now go to Dashboard -> Appearance -> Menu
4. Enable the CSS Classes option under the Screen Option settings
5. Add the respective CSS class name ( which you entered in step 2 ) under the selected menu element.