For this you will need Form Builder, DataAssist and Universal Email and possibly SecurityAssist.
To sttart you will need to configure the user registration table. In addition to the usual columns for a user table, there will need to be two additional column. One column for the registration status the default value for this column should be 0. The other to store a random string.
Use Form Builder to create the initial Registration form.
Use DataAssist to store the registration information in a database. The Users status will automatically get set to 0, you will need to generate a random string to store as well. You can use the SecurityAssist random password function for this.
Use Universal Email to send the email. The email will contain a link with 2 query string variables:
the id variable will be the primary key ID value for the user that registered. The regCode will be the random string that was stored in the.
On the confirm.php page, crate recordset to filter the users table based on the ID and regCode passed in the link to find the users record, then use the dataassist Update Record server behavior to update the UserStatus column to 1