Answer
Go to the ‘Forgotten your password?’ link on the Sign in page.
Background
To complete your user registration on the platform you must first verify your email address by using the activation link that will be emailed to you. This process is used to ensure that your user account is linked to your email address. The activation link can only be used once and so the activation link may fail if you have already tried to use it before.
Steps
1. Go to the ‘Forgotten your password?’ page from the Sign in page
2. Enter the email address that you used to register and an activation email will be sent to your email address