Quest #063 Keep Your Eyes Peeled - Swinedimples Academy
Quest Requirements: Read the red sign post in West Wormwood
Quest Pre-Requirements: Have 30 Points in Sword Skill Tree
Reward: Warrior's Sword
This quest begins by speaking to a man in the Swinedimples Academy church which is on L1 of the northern most building. In order for him to offer you this quest you must have at least 30 points into the Sword Skill Tree.
I can't think of any way for you to reach the island in Western Wormwood that this quest requires without the Starflight Express which you get after completing Side Quest #039. Basically the Starflight Express allows you to fly around on the world map and land anywhere - in the case of this quest you'll want to land on the island in Western Wormwood. This location is pictured in both of the screen shots below.
On the southern part of this island you'll find a red sign which you can't miss. Inspect the front of it as well as the back of it then Zoom back to Swinedimples Academy and turn the quest back into Marco. Speak with him again for Sidequest #064.