Send freeform email notification to manually entered recipient address
The recipientsEmail field should be an Email fieldtype, and in Composer you need to set the notification template in the Field Property Editor column (on right) for that field and it'll send an email to the email that is entered in that field when the form is submitted. :)

View the documentation page here for more information about email notification options:
https://solspace.com/craft/freeform/docs/email-notifications/