How to call modal box by a menu item
1. Creating menu item
Open admin panel and click “Menus -> Main menu -> Add New Menu Item” in the top menu.
Now you should add the contact form or callback module to the site pages. Open Module Manager (“Extensions->Modules”) and choose your module. In the “View options” section find drop-down list (“Open Pop-Up/Callback window by”) and select “Class” option.
Then go to the “Menu Assignment” tab and choose pages to display (it should be “all pages” possibly).
After that put the module in any position (Warning! Position must be used in the template) and select “Published” in the “Status” drop-down box.