There is good document available on portal for upgrade. Please refer below links.
Upgrading DevTest - DevTest Solutions - 10.1 - CA Technologies Documentation
And refer below for more details upgrade center.
DevTest Solutions Upgrade Center
On sidenote, please make sure you take backup of your all customized Devtest properties files and external files (jar,exe,libs etc). And Plan to update features which are sunset.
Hope this helps.
Thanks,
Rajesh K Singh