They are usually eat them raw, just peeled, sliced and added to a salad. You can also cook them there used in Indian dishes often.Kohlrabi can also be steamed or boiled, don’t peel until after they are cooked. Steam or boil until bulbs are tender, peel skin, and season depending on what you can drizzle some olive oil or butter and some salt and possibly dill if you can. If the leaves look nice and green chop them up and saute them for  3 min and add them in. Treat it kinda like cabbage if you would cook or eat cabbage in a dish then you can be making it pretty much the same cept the  peeling part when cooking.
You can saute it
Peel the tough outer skin from the kohlrabi, then coarsely grate the bulbs. In a skillet, heat butter and olive oil. Add garlic,and kohlrabi and saute, stirring for 5 to 7 minutes until kohlrabi is tender crisp FriesPeel and slice raw kohlrabi into thin matchstick-sized strips. Spreadout the strips in a single layer on a baking sheet. Drizzle with oliveoil, and season with salt and pepper if desired. Bake 20 to 30 minutesat 400 degrees until the kohlrabi softens slightly, but still has alight crunch