I have photos of a product and I would like to create a white background behind it. Like it is done in this example:
I have tried playing with levels and the brightness but that also messes up the product itself. How do i do this?
You don't do it in Photoshop. You start in the "studio".
This website explains a lot of jewelry photography.
When photographing pearls, by using only one light source positioned above, the pearls will appear rounder with more dimension.
Assuming you don't want to photograph pearls, take with you that they are using a single light on top, with a lightbox all around it. If you don't have a flash with a diffuser slightly larger than your subject, you could use some other lamp. If you don't have a lightbox, you could buy one (cheap), or you can use some white paper to reflect the light onto the subject.
Use a white acrylic sheet as your surface. (Or paper). Adjust your exposure so that the background is already almost overexposed.