Soft proofing is an option that allows you to simulate on your computer monitor what your print will look like when it is printed on media using a specific ICC profile. When a printer profile is made the color of the paper or fabric media is one factor that is shaped in the profile, because of the ink and the media combination. Using the 'Soft proofing' simulation option you can select your custom profile the view the simulation.  Before doing it, make sure your ICC profile is installed in neoCatalog.

Once you are in the Detail View of one colorway, from the lower options choose 'Soft Proofing', which allows to set up the proofing and enables the proofing for every single Colorway.

Selecting 'Proof Setup' opens a dialog where you can choose one of your installed ICC profiles and select the supported rendering intents Absolute colorimetric, Relative colorimetric, Saturation, or perceptual with their display options. 

Once the setup is done, select 'Proof Colors' from 'Soft Proofing' to enable the simulation and the proofing will be applied.