Hi,
Thank you for posting in Symantec community.
I would be glad to answer your query.
If Symantec Endpoint Protection Manager is installed then need to install now SEP clients on the network computers.
You should refer this article:
Symantec Endpoint Protection 12.1: Installing the Manager for the first time and deploying clients
http://www.symantec.com/docs/TECH163580
Following articles will help the the info which you are looking for.
Creating custom client installation packages in the Symantec Endpoint Protection Manager console
http://www.symantec.com/docs/TECH102817
How to Deploy Symantec Endpoint Protection to your client computers using the Migration and Deployment Wizard.
http://www.symantec.com/docs/TECH102907
If you could provide the following info we would be in a better position to assist you further.
1) Symantec Endpoint Protection Manage (SEPM) version.
2) Total number of clients in the network. Currently is there any other AV running?
3) Planning to install SEP clients on total how many computers?
4) Are there any remote sites?
5) Planning to install on Servers, if yes what's the OS?