In episode 63 of the 2011 anime, titled Gon and Killua officially begin their grueling training under Biscuit Krueger during the Greed Island arc . Summary of Key Events
During a task where they must dig through rocks to make a straight path to Masadora, Gon and Killua learn Shu —a Nen technique that extends one's aura into an object to make it an extension of their body. Hunter X Hunter 2011 Episode 63
To continue their training, Bisky makes the boys travel 70 kilometers to the town of Masadora and back. In episode 63 of the 2011 anime, titled
Witness the start of Bisky's intense training and the boys' development in these episode highlights: BINOLT!! | Hunter X Hunter Ep. 63 REACTION & REVIEW!! YouTube · BOLDcast Hunter X Hunter 2011 Episode 63