You would need Security Assist, Data Assist, and Universal Email.
This is how the user registration starter pack was created. You need to add a boolean "emailVerified" field to your table as well as a "VerificationCode". You can use security assist to generate a random string that you can store in the user record when registering using the dataassist insert server behavior and set the emailVerifed field to false or zero.
Then use Universal Email to send an email to the user email address that just registered. Include in it a link back to your site that includes the email address and verificationCode as url parameters. The page that it links back to can just have the text "Thank you for verifying your email address". It would have a recordset on the top of the page that would filter by the email address and verification code included in the url and return the record ID of the verified user. Then use DataAssist to update that user record and mark it as verified on that page based on the trigger that checks to make sure that recordset is not empty.
