https://www.epo.org/en/node/i-already-have-epo-smart

I already have an EPO smart card. How do I start using two-factor authentication?

Go to the EPO sign-in page

Select Sign in using smart card. After entering your email address, you’ll be asked to set a password. Then you must set up one or more second-factor authentication methods. 

During this process, you'll be asked to accept our terms and conditions. You'll also be able to consult our data protection and privacy policy

Once you've set up two-factor authentication, you can sign in using two-factor authentication or your EPO smart card (which you can use, unless it has expired, until the end of 2024).