What is the best way to build MVVM model interaction with nHibernate entity?

Question

NHibernate

Given:
- model for MVVM;
- entity nHibernate;
Question: how best to build interaction between them?
I found an example on codeproject, where the model and the entity are 1 and the same class.
www.codeproject.com/Articles/424337/Tasks-managing...
This option seems to me not very convenient (correct), since we are mixing MVVM and working with the database.
Prompt the best architectural decision, for the task.