Pinch each stem just above any leaf node. The leaf nodes are the little swollen-looking parts where the leaves emerge from the stems. You decide which
leaf node to make your pinch above by imagining the point at which you want your plant to bush out, or create new stems. I think, for a wandering jew, that you might want to select a leaf node that's about 4 to 6 inches above the soil level.
You don't have to pinch all of the stems at once. You can do just a few at a time, so that your plant doesn't suddenly look like nothing but little stubby stems sticking out of the soil. In fact, since you seem a bit hesitant about the technique of pinching, why not just do one stem? Then you can wait a few weeks and see how the new little side shoots begin to appear on that stem, just where you pinched it off. Approaching it slowly that way may help you feel more sure of what you're doing, and you won't have to worry about ruining your plant.
Here is a video that might help you:
In the video, the woman is using pruning shears (also called clippers), because she's working with plants that have thicker stems than the one you want to pinch. For soft-stemmed plants, such as a wandering jew, I just use my fingernails, but you can use a small scissors, if it's easier for you. The close-up views of where to make the cuts/pinches are at the end of the video.
"Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?" - Douglas Adams