Travel to Moonglade and speak with Dendrite Starblaze in the village of Nighthaven.
You're now ready to learn about poisons and the power we as druids have over it, [player]. Cenarius has blessed us with the ability to purge even the most foul of poisons with but a mere incantation. This gift is not to be taken lightly... and to ensure you learn this lesson, you'll work to address the affects of poisonings as a layman would.
Travel to Moonglade and speak with Dendrite Starblaze; he awaits your arrival to begin your lesson.