In Depth Book 2 Epic Quest Guide - Looking for a complete Lord of the Rings Online walk-through? Killer Guides can help you (in case they release additional LotRO class guides, probably their Allods Gold guide set is also worth a try in the future).

[26] Foreword: Aiding the Order - Gandalf awaits you inside the Prancing Pony. He suggests that you seek out Radagast the Brown in Ost Guruth. Ost Guruth is a city located deep in the heart of the Lone lands. 

First you must travel to the Ost Guruth. Follow the South Road leaving Bree heading east until you reach the Forsaken Inn. 

From the Forsaken Inn continue east until you reach Ost Guruth. Radagast the Brown is at North end of this town inside a building on the second floor.

[26] Chapter 1: The Red Swamp - Radagast asks you to bring him the moss of the Bog Prowler nests in the swamps to the east. Leave Ost Guruth and head East into the Haragmar. 

In the swamps you will find moss that you must collect. Bring back the moss to Haragmar. Reward: None

[28] Chapter 4: The Stone-speaker - Radagast asks you to speak with Aric the scholar.  He is located at a small encampment in the Southern Harloeg. Reward: None