You can accomplish this with an automation. When a new form submission is populated in the Forms table, the automation will find the matching record in the People table and then link the two records. The finished automation will look like this:
You will first want to create a field to accept the customer’s email and a new linked record field in the Forms table.
Now you can start building the automation. The trigger is a new record being created in the Forms table.
The first action we want to run is “Find Records”. This will find the customer in the People table based on the email address they submitted on the form.
Under conditions, we’re saying only return the record in the People table who’s Email field matches the Email field in the Forms table.
Now that we found the matching customer record, it’s time to link the records. Add a new “Update record” action after the “Find records” step.
Here we’re saying go back and find the record ID of the new form submission that triggered the automation and then put the record ID of the matching customer record we found into the linked field in the Forms table.
Let me know if you need help with any of these steps!