How can i use any imported model(for example Crysis Nanosuit) instead of mecanim rigged model?

Recently i've been following a "Stealth Project" tutorial provided by Unity officials and following it alongside with the downloaded project ( Stealth Project- https://www.assetstore.unity3d.com/en/#!/content/7677) . Tutorial link - https://www.youtube.com/watch?v=ZoTr3mPpPSY∈dex=10&list=PLX2vGYjWbI0QGyfO8PKY1pC8xcRb0X-nP

QUESTION ::: How can i use any imported model(for example Crysis Nanosuit) instead of Ethen ? Please looking forward to getting some help.