Use warm water with some mild liquid soap, and submerge your garment in the water and let it soak for about 4 minutes. Then, carefully rinse the garment in warm water. When you're done with rinsing, squeeze as much water as you can from the garment.
Then, lay the garment out on a flat surface and let the natural process of drying take place.
Note: Do not dry in a dryer/tumble dryer and remember not to twist or wring the garment as you'll potentially damage its shape.
We also suggest going to a dry cleaners as they are experts in taking care of luxury knitwear. Their experience means your sweater will be in the best possible hands.
If you notice little balls of fibres forming, don't worry. It's what you call piling and it's a completely normal process that takes place during normal wear and cleaning. You can easily remove these little balls of fibre by pulling them gently.