How do you sleep train 13 months baby?

Hi mummies my baby is used being rock n cradle to sleep during nap and bedtime. I tried to leave him alone but he will cry murder. Tried to pat him to sleep but it will be almost 2 hrs and i gave up already. He will be wide awake by then and start playing in the dark. Will i still be able to train him cause he will be entering childcare once he hit 18 months. I really need help? Will hire sleep consultant works? Anyone hire before? Thanks alot mummies.