Vector3 NpcLoc = ObjectManager.GetWoWUnitByName("TheNPCName").FirstOrDefault().Position;
wManager.Wow.Bot.Tasks.GoToTask.ToPositionAndIntecractWithNpc(NpcLoc, 1111, -1, false);
1111 being the npc ID, -1 is gossip option
edit: keep in mind i haven't touched the api for couple months so it may cause a error if you use this code. I don't remember everything anymore