Hello,
I have test your site and found that the CSS Classes (optional) field was not shown because the “Custom Clases” option was unchecked from the screen options from Appearance >> Menus.
Now I have checked that option and it is shown now. Also for the newsletter you just have to use “woodmart-open-newsletter” class.
Screenshot: https://jmp.sh/fCHHPdE
Yes, our theme works with WPML plugin. I thought it’s the same plugin, I searched about this topic and came to know that inside the WPML plugins there is some shortcode for enabling the currency switching functionality.
You can check the below article for clarification: https://wpml.org/forums/topic/shortcode-currency-switcher/
Best Regards.