It’s a catch 22 scenario, you want to run your vCenter server in a cluster with EVC enabled, but you can’t build/manage a cluster without vCenter running so here is how you do it.
1) Build vCenter on ESX server 1
2) Build a cluster in vCenter, enable EVC and place ESX Server 2 in that cluster.
3) Power down vCenter Server(s),. open vSphere client, connect to ESX server 1, remove the vCenter VM(s) from inventory (DO NOT delete from disk). close vSphere client
4) Open vSphere client, connect directly to ESX server 2. Browse the datastore for the vCenter VM(s). Connect to them, power them up.
5) You can now connect to the vCenter and move ESX server 1 into the EVC cluster.