heh...I know what you mean about the help docs. I love when there's a text box labeled something like "Settings" and the help file says, "This is where you put settings." Really?
I just realized I answered not knowing which version of ePO you're on. I'm running ePO4.0 and when I open the policies for HIPS 6.1 and 7.0 Firewall Options the setting is right there. I can't remember what 3.6 looks like. Have you kept the HIPS extensions current along with the client packages?
As far as agent communication goes, a wake up call should do the trick, especially if the policy has been modified. I have seen wake up calls that just resulted in "No package to receive" and nothing happens. But if the policy's been modified it should download and enforce the new policy package.
Aside from that there's the McAfee Agent policies which specify how often to check for new policies/tasks (ASCI) as well as how often to enforce the currently downloaded policy package.