To make sure the years of enjoyment from knitwear, you should understand how important it is that you wash garments correctly. Woollen garments have to be washed by hand at low temperature, otherwise, machine wash will destroy the wool or the garment will shrink of felt. 

Use detergents specially made for wool. Use plenty of water and wash the knitwear inside out. Squeeze the garment gently. Do not rub or wring. Don't soak the garment too long in the water. To make the garment bigger you can stretch it into the bigger size by drying it flat. Do not hang! You can spread out any wool garments on a towel to dry. Do not dry it in direct sunlight. Store it by folding the garment than hanging it.