Nemarti is one of the Combat instructors, known to be the instructor of both Ranged and Fletching. She is located north of the Lumbridge Castle. While she is most likely intended to help new players, she gives information about Ranged in combat.
She gives out a training bow and 25 training arrows to any player every half an hour, unless they had the arrows and bow in their inventory or in their bank. Players could either take the bow and arrows from her, or take air and mind runes from the Magic combat tutor nearby.
As of an update on 17 August 2017, players can toggle whether they want ammunition on the ground to automatically be equipped or remain in the inventory when picked up.