Notes:
The following steps could differ slightly depending on your Email Provider.
The following steps use the MailChimp as the Email Provider.
Ensure that a custom field is already created in your Email Provider's account.
Open the Email Optin module's settings
In the Content Tab → Email Account, choose your preferred Email Provider
In the Content Tab → Field, enable the Use Custom Fields option
Click on the Plus icon
to add a new FieldUnder the Field option, choose the custom field you want to use
Expand the Field Options group
Ensure that the field type is Radio Buttons
In the Options field, click on the Chain icon
to add the link
Ensure that the Required Field option is enabled
Pro Tip: If you don't want to show the field title, in the Field's settings, go to Advanced Tab → Custom CSS → Free Form CSS and add this CSS snippet:
selector .et_pb_contact_field_options_title {
display: none;
}