You can register a virtual machine to the Inventory in vCenter Server/VirtualCenter or in an ESX/ESXi from a command line.To register a virtual machine in vCenter Server:

1. Open the vSphere/VMware Infrastructure (VI) Client and log in with appropriate credentials.
2. If connecting to vCenter Server, click on the desired host.
3. Click the Configuration tab.
4. Click Storage.
5. Right-click on the appropriate datastore and click Browse Datastore.
6. Navigate to the folder named after the virtual machine, and locate the virtual machine.vmx file.
7. Right-click the .vmx file and click Add to inventory. The Add to Inventory wizard opens.
8. Continue to follow the wizard to add the virtual machine.

To register a virtual machine from a command line in an ESX host:

1. Log in as root to the ESX host with an SSH client.
2. Run the command:
   
   # vmware-cmd-s register full_path_to_virtual_machine\virtual_machine_name.vmx

To register a virtual machine from a command line in an ESXi host:

1. Log in as root to the ESXi host with an SSH client. For information on using Tech Support mode, see Using Tech Support Mode in ESXi 4.1 and ESXi 5.x (1017910).
2. Run the command:
   
   # vim-cmd solo/registervm /vmfs/volumes/datastore_name/VM_directory/VM_name.vmx

Thanks

WintelAdmin