Assuming here that your ESXi environment is already nested and configured appropriately.
Power Off the guest ooerating system you want to enable FT for
Disconnect the CD / DVD (or select client devic eoption)
GO to options tab and sele the Advanced / General Button
ON right hand side click configuration parameters button
Add 3 ROWs
Name: replay.allowFT Value: true
Name: replay.supported Value: true
Name: replay.allowBTOnly Value: true
You ned VT-X as a feature of you rphysical CPU adn this needs to be passed through to your Nested ESXI host.
http://www.virtuallyghetto.com/2012/08/how-to-enable-nested-esxi-other.html < See this blog for more details.
It matters greatly if you are using ESXi 5.0 or 5.1