Create a duplicate detection rule
1. Go to form explorer.
2. Select the form you want to create the duplicate rule for, then click on ‘Rules -> Duplicate Rules’ menu item from the toolbar.
The duplicate rule designer opens with a single rule created for you.
4. Add a rule name in the description box.
5. Add rule. To Add rule:
a. Select a field from the list
b. Select operator
c. Enter message to show to the user