Two-handed Sword is crafted with Blacksmithing in Mabinogi (weapon). This page lists everything needed to make it, checked against the game as it exists today. The interactive planner lives in the Blacksmith Companion.
How to get the manual
The manual is rank 4 and survives 30 uses; every crafting attempt spends one use.
Gilmore: general shop owner in Bangor, sells them at his counter (66,000 gold).
Prairie Dragon: field raid boss northeast of Maiz Prairie in Rano. No requirements; fight it northeast of Maiz Prairie in Rano during twice-daily spawn windows.
Lileas: Jousting Arena Manager in Tara. Trade Jousting Points at her shop for manuals (66,000 gold). Spend Jousting Points at Lileas's shop by the Tara jousting arena, earned from matches there.
Materials
Expect about 4 attempts per finished item (32% average progress per attempt). Per-attempt materials are consumed on every attempt; finishing materials once per item.
Each attempt uses
4× Iron Ingot — refine from Iron Ore (common low-rank Refining output)
4× Silver Ingot — refine from silver ore. Mine it in Barri Dungeon or north of Tory Ravine