sorry, under the vCenter Server .iso there is a Vmware-Licenseserver.exe file under the vpx folder, you can install it that way.
Also, you can confirm whether you already installed the license server, by checked the services of the vCenter Hosts Server. There should be a VMware License Server Service present and it should be started.
Once you confirmed you have a license source setup, you can point your ESX Hosts to that source through the Confiuration Tab and licensed features on the ESX Host(s)
Also, through you vCenter Server you should have an Administration button and a licenses tab