Hello,
You can change the font by means of the Advanced typography option, which allows you to choose the item from a drop-down or insert your custom CSS class. Please navigate to the Theme Settings > Typography > Advanced Typography.
Here is the documentation providing more detailed instructions: https://xtemos.com/docs/woodmart/advanced-typography-settings/
Please add this code to the Theme Settings > Custom CSS > Global:
.wd-sub-menu li a {
background-color:red;
}
Best Regards