http://service1.symantec.com/support/ent-security.nsf/docid/2008032202341548
Following that article to setup the replication server. Once that is done and you have 2 SEPM servers on the network.
Open up the SEPM on the primary server (original) and go to ADMIN in the SEP console.
Under Admin, go down to Servers on the left side.
Choose your site (local site- most likely) and below that "add existing replication partner" if yours is not already in the list of servers in the left pane. If it, "edit site properties" and configure the order in which the clients will be reporting to the servers, in case one goes down the other will be communicated to.
That should work.