After vSphere Fault Tolerance has been turned on for a Primary VM, you can change the host its associated Secondary VM resides on by migrating it.
Prerequisites
Launch the vSphere Client and log in to a vCenter Server system.
Procedure
Results
The Secondary VM associated with the selected fault tolerant virtual machine is migrated to the specified host. Note that the Primary VM can always be migrated using the Migrate command in its context menu.