Just complete the registration form shown on application shown at the launch of PSE 3.0. On submitting it, an unlock code will be send to you at the email you provided on the registration form.
Now, just use that unlock code to unlock your app.
When you launch Starter Edition, it will prompt you to register.
Just follow the on-screen instructions.
Be sure to use the same email that your wife used to get the code since the code is tied to the email address.