Hello, Rachanee!
Make sure the installed plugin is activated, once it is, you should be able to find the “Checkout Fields” under Bookings tab. If it is not there, try navigating to the following URL directly: your_website_url/wp-admin/edit.php?post_type=mphb_checkout_field
If the issue persists, submit your request to our Help Desk providing a temporary access to your WordPress dashboard, so we take a closer look at the issue.
Regards,
Andre