How to create a symantec endpoint management server for deploying anitvirus signature file for clients at new site?

You create a Symantec Endpoint management server simply by installing the management console on a server and then attaching the clients that you want to manage to that server.  If there's a server at the site, then you should ideally use that local server to manage the SEP clients including definition updates.  If not, then you could install the software from a server at a different location (i.e., the home/central office) by deploying them either using the standard method through a VPN connection, or by email as remote clients. However, in the second situation, the users need to have administrative access to their computers to install the software. Here's a forum post that has links to articles to help you set up the remote install if you aren't familiar with it:

http://www.symantec.com/connect/forums/remote-client-deployment-over-internet

If you don't want them to have to check in with the server on a regular basis to get antivirus definitions, you can deploy them as unmanaged clients. In that case they can be set to download their definitions directly from a Symantec server on the internet.