Step 1: from within the vSphere client, while connected to vCenter1, select the VM and then from "File" menu select "Export"->"Export OVF Template" (Note: make sure the VM is Powered Off otherwise this feature is not available - it will be gray). This action will allow you to save on your machine/laptop the VM (as an .vmdk, .ovf and a .mf file).
Step 2: Connect to the vCenter2 with your vSphere client and from "File" menu select "Deploy OVF Template..." and then select the location where the VM was saved in the previous step.