Calculate NEF of an amplifier
I don't think that ADS has a built in tool for measuring NEF. You'll need the equation for calculating the NEF (noise efficiency factor) and will need to compute it by entering the equation into ADS. This is usually done in the data display window. 

I found the equation describing NEF in a paper by Somak and Hall, see equation 1. It appears that NEF is a function of the input referred noise which is described in equation 3.