Speak with Madelle, the Conjurers' Guild Receptionist, in Old Gridania at X6-Y11. Make your way to the nearby Guildmaster of Stillglade Fane, E-Sumi-Yan, who's meditating within. E-Sumi-Yan will explain the principles of Conjury and will then ask you to vow yourself to nature. Do so.
In the same pattern as Way of the Lancer, you must leave Gridania and head to the Central Shroud to kill Squirrels, Ladybugs, and Funguars. Head to the Blue Badger Gate at X14-Y-14 in New Gridania to leave the city and find your prey in the Central Shroud.
The Squirrels and Ladybugs can be found at X23-Y16, and the Funguars can be found a little further south at X23-Y17. Slay 3 of each and head back to E-Sumi-Yan to complete the quest.