How to reregister

I got free avast antiviruis.
No it is telling me, registration expires in 38 days. But there is no button, link etc to reregister.
In settings I also just find the info, but no link, button etc to reregister.

What to do?

I think from memory the registration button appears once there is 28 days left to go.

http://www.avast.com/en-us/registration-free-antivirus.php

Correct.