You can download Notification Server Console 6.5 from the following site:
When installing the Console 6.5, both of the following files need to be installed (in this order):
(Note: Altiris_ConsoleLP_6_5.exe and Altiris_ConsoleDataLP_6_5.exe are the Language Packs that also can be installed with the two above.)
Or you can download from the Altiris Console you currently have. Go to the Configuration tab > Configuration > Upgrade/Install Additional Solutions > Available Solutions > Segments > Notification Server Upgrades and Updates > Altiris Console 6.5.