You've probably meant "how to add an attribute, for example VSA"
So under:
/localhost/Radius/Profiles/Test-Profile/Attributes
use:
set Cisco-SSG-Account-Info test
(or any other attribute, in this example Cisco VSA was used)
--> ls
[ /localhost/Radius/Profiles/Test-Profile/Attributes ]
Cisco-SSG-Account-Info = test
The excerpt from user guide you have provided is used in TCL scripts and it's not relevant to your problem.
I assume you already have your VSA defined in attribute dictionaty.