When you use an Amawrap, you are allowing for true skin-to-skin contact. This contact produces a hormone in your system called Oxytocin (aka the "love hormone"), which helps your breastfeeding success (read more here)
To breastfeed in the sling, simply loosen the double knot, feed some fabric through, then re-tighten the double knot. With the loosened fabric, lower baby, then latch them on! Once done, make sure you tighten the wrap back up.