Linen is a very durable fabric, and has been used in garment manufacture for centuries. It is smooth, making the finished fabric permanently lint-free, and will become softer and softer the more it is worn and washed.
Use a clean sink or other large basin filled with cold water. Put in a small amount of gentle detergent such as Earth Choice Wool and Delicates Wash (or baby shampoo). Gently swirl the linen in the sink or softly knead it (like you're kneading bread). Rinse thoroughly with water and remove excess water. Hang on a coat-hanger, ironing out any creases with clean hands, and leave to dry with plenty of ventilation.
We recommend you handwash your Milk Linen garment as it is the best way to ensure it is gently cared for. We also understand that busy parents sometimes don't have the time!
Conveniently, every Milk Linen garment comes with a linen wash bag (which is also fabulous for storage). If you need to use a machine, always wash separately in a cold gentle cycle with the garment inside the wash bag and the drawstring pulled closed and tied.
Use a small amount of gentle detergent such as Earth Choice Wool and Delicates Wash (or baby shampoo). After the gentle cycle is finished, ensure all detergent and excess water is removed, and hang on a coat-hanger, ironing out any creases with clean hands, and leave to dry with plenty of ventilation. 
Martha Stewart is our domestic goddess go-to..
"If you stain a washable garment, the golden rule is: Act quickly. For a liquid, gently blot up any excess with a white cloth, working from the outside in, so you don't spread the stain; do not press hard or rub."
"Always test stain-removal techniques in a hidden area of the garment, like an inside seam. There are no guarantees -- sometimes stain-removal techniques do more harm than good -- so if you have a particularly vexing stain or a valuable, delicate piece of clothing, take it to a professional."
Here's an article on spot cleaning which may also help!
One of the inherent and beautifully unmistakable characteristics of linen is that it wrinkles. The tendency to wrinkle is often considered part of linen's particular beauty and charm. 
Milk Linen garments are designed to be air-dried on a clothes hanger (see above instructions) and worn without the necessity of ironing. However should you wish to maintain perfect smoothness of the fabric, you may prefer to iron on low heat when the garment is still slightly damp.
We want you to enjoy your beautiful Milk Linen garment for as long as possible! Please note consistent exposure to hot ironing or aggressive laundering can lead to breakages in the natural linen threads.