You need to get software for the upgrade. In order to get the software you need download access to support.
Sounds like you already have that.
The upgrade itself is not tied to any account. A user name and email is asked during the install for the record just in case something goes wrong and a support case is opened and the support needs to contact for more information. The user name and email may also be dummy ones.
See the documentation for upgrading
CA PPM - CA PPM - 15.6 - CA Technologies Documentation
This discussion board has also plenty of threads on upgrade and install if you just search.