I have 200 pc with mcafee enterprise 8 installed, and epo 4 server.
how can i confirm that every thing is working good, and the agents are getting update and all the pc is getting update from the epo ?
You to have the ePO client on every PC - this will report back to the ePO server on the PC's status.
Genrally you install the ePO client (using AD-GPO/WPKG/manually...) then the ePO client installs the relevant anti virus software.
In your case maybe this is already setup and you just need to log into your ePO server to see the status of you clients. If not try McAfee support or the ePO forums http://community.mcafee.com/community/business/epolink text
It's been a few years since I used EPO but as far as I can recall all that information is available from EPO itself. If in doubt, read the docs.