You can buy the expansion from a retailer, or it's available from within your Guild Wars client by clicking on the Guild Wars Store icon. Purchasing the expansion this way will take effect immediately, allowing you to instantly explore the new content in Guild Wars: Eye of the North.

Each main town from the three existing Guild Wars chapters will have a new NPC (Non Player Character) - you'll need to talk to them to receive the mission which takes you to Eye of the North:

Characters from the original Guild Wars Prophecies campaign should seek out Len Caldoron in Lion's Arch and accept the What Lies Beneath quest.

Characters from Guild Wars: Factions should seek out Minister of Maintenance Raiugyon in Kaineng Center and accept the Feel the Earth Move Under Cantha's Feet quest.

Characters from Guild Wars: Nightfall should seek out Bendah in Kamadan and accept the Hole of Istan quest.

Once you have completed these missions you will find yourself in Boreal Station. You will also notice new purple Asura Gates have appeared on the map - these can be used to transport you direct to Boreal Station in the Eye of the North at any time.

Within Eye of the North there are 4 new Title Tracks - Asura, Deldrimor, Ebon Vanguard, and Norn. By undertaking quests for each of the groups, you can gain reputation points, which will increase your rank in the new Title Tracks.

Once you have gained 1000 reputation points, you will reach Rank 1. You will now be able to gain a special Status Effect which will provide bonuses when exploring. As your rank in a Title Track increases, you'll also open to access to new services:

Rank 3: Access to a special item crafter. Each group has a single item crafter who provides unique and powerful items. You must spend a Skill Point to have these items crafted for you.

Rank 4: Access to an exclusive weapon crafter. Each group has a single weapon crafter who provides unique weapons, such as the Raven Scythe and the Charrslayer Axe.

Rank 5: Access to an exclusive armor crafter. Each group has a single armor crafter who provides single unique armor pieces, such as the Dread Mask or the Magma Gauntlets.

As your Rank increases, so do the bonuses granted from the special status effect your character receives when displaying the Title. There are also 50 new PvE skills in Eye of the North, which can be gained by completing quests for each of the groups.

These skills and bonuses will also become more powerful as your Rank in the relevant Title Track increases. Through these new Title Tracks, the Eye of the North expansion provides a lot of extra content and challenges.