From ColorWiki

This shows how to simulate what an image will look like when it gets printed using the custom printer profile from CHROMiX. You can soft-proof an image using a feature in Photoshop, or you can “hard-proof” – actually make a print on one printer which simulates the output from a different printer.

Proof on the monitor (soft proofing)

1. Open the image in Photoshop
2. Choose "View > Proof Setup > Custom..."
3. Device to Simulate: Select your custom CHROMiX profile
4. Leave “Preserve Numbers” unchecked.
5. Intent: Choose Perceptual or Relative Colorimetric, whichever you are using when printing (See Appendix B for more information on rendering intents)
6. “Black Point Compensation”: √ checked
7. Paper Color: unchecked; Simulate Ink Black: √ (checked)
8. Click OK

The image on the monitor will be displayed through the same profile you will use when printing. This provides a more realistic expectation of the colors you will see on your print, because the display will be limited to the gamut of your printer.

You can use a press / proofer profile for this simulation, or your printer profile. In both cases Photoshop will display your image as if it had converted through the profile (as in the example above) and then “proofed” back to your monitor. This is the most common use of soft-proofing.

Proof on a printer (hard copy proof)