Hello,
First of all, you need to create the Product category menu in the Appearance > Menu.
Then you need to switch to the mobile view of the Header builder: https://xtemos.com/docs/woodmart/header-builder/header-responsive-settings/
Enter the mobile menu element and field the option to show the Category menu, as soon as you enable the option the drop-down with all the menus created in Appearance > Menu would appear.
If you have any questions please feel free to contact us.
Best Regards