Mystery resolved. Yes, you can wash your jeans but with certain ways to protect them from damage.
This video is a good tutorial to show you how to do that. You can do it with handwash or just throw them into the washing machine, we strongly recommend using a laundry bag to wrap your jeans if you use a washing machine.
You also need denim soap or detergent. For the first time wash of your jeans, use white vinegar instead, then use some detergent to help clean the vinegar out of your jeans.