Basically (naturally, there are numerous variations to this theme...) the procedure looks like this (I'll assume that the vCenter Server has already been installed, i.e. that it is working):
- add a virtual machine (as usual - using "File" -> "New Virtual Machine" procedure)
- when the installation has ended, power the newly installed VM off and the desired ESXi host on
- after the host is started, right-click on the VM and select the "Manage" submenu, then select "Upload"
- the previous step should open the "Upload Virtual Machine Wizard" - you should now select your vCenter as the destination server
- select a Destination Location (this is the desired Datacenter)