When you prefer the outcome on the right, click to the right of the midpoint, with the distance from the center in proportion to the ratio of the difference in utility between the outcomes relative to the biggest difference (between the utilities of WIN $100 minus LOSE $100).
When you prefer the outcome on the left, click to the left of the midpoint with the distance from the midpoint in proportion to the difference in utility relative to the biggest difference.
When the two are the same, leave the mark at the midpoint or drag it to the midpoint.