How Can I Add OnClick Event To A Specific WordPress Menu Link

This is not really a WordPress specific question, but since WordPress does not provide customization for menu items, I think you’re gonna need this.

You can use .bind() in jQuery to add an event to user’s click on an specific item. Take a look at this:

jQuery(document).ready(function(){
    jQuery( "#menu-item-57" ).bind( "click", function() {
        goog_report_conversion ('tel:800-123-4567');
    });
});

Change the menu-item-57 to whatever ID of the menu item you want to bind a click event to.