After creating list and adding emails / IP address to list, you still need to apply list to Gravity Forms form field.
Open Advanced tab of the field you'd like to apply list to on Gravity forms form edit page
You may customize the validation message that to be shown in front, if leave it blank then the validation message in form settings will be shown.
Choose action for list
Both email list and IP list can be used as blacklisted or whitelisted.
Choose Block to use it as blacklisted. If field value MATCH keyword in list then the actions you chosen on form settings page will be triggered.
Choose Allow to use it as whitelisted. If field value DOESN'T MATCH any keyword in list then the actions you chosen on form settings page will be triggered.
You may apply IP list to any field that you'd like to show validation message there.
Update Gravity Forms form to save what you set to the field.
Purchase Gravity Forms Blacklist Pro