This is how I use my Silhouette to layout pages on a sketch. I learned this from Kelley at findingtimetocreate.blogspot.com.
In a nutshell, I open the jpg of the sketch in Silhouette studio, and blow it up to 12x12. Then I just take the elements I'm cutting with the Silhouette and "trace" them as they appear on the sketch. Then I color code them -- these were not necessarily the colors I was using for the LO, but I cut everything that I had colored brown out of the same sheet of paper, everything white out of another, etc. The end result (as seen in my gallery) is pretty close to what I placed in Studio.