Hi,
Thank you for posting in Symantec community.
I would be glad to answer your query.
You have mentioned that you want to edit policy so that client will take definitions from liveupdate sever (Internet). What's the default source of update for this client?
Was this client working as a managed client then converted to a unmanaged client and now want to access liveupdate tab which is grayed out? Any changes made in the SEPM console won't be applicable for unmanaged clients.
If SEP is installed as a unmanaged client then liveupdate tab shouldn't't be grayed out. Once you click on liveupdate it should get connected to the internet.
If planning to install SEP 12.1 client then refer the following article
How to change the LiveUpdate source of an unmanaged Windows Symantec Endpoint Protection 12.1 Client
http://www.symantec.com/docs/TECH166129