ArenaNet are creating a series of events to entice you back into Tyria and they release coming back to a game that has had so many updates and changes since a year ago let alone release may need some adjusting to. So to assist you they have programmed in some livestreams, written guides to be released, free or discounted items in the Gem Store to help you on your way!
First things first, you can unlock the first episode of the Living World Season 4 for free in the Gem Store, it is called "Daybreak" so don't miss your chance in doing this. You can also get a free Tradesman's Package this week too in the Gem store and this has a limit of one per account. Both of these items will be available from 1st April so don't wait around, log back in and claim those freebies and to unlock Living World Season 4 you will need to purchase the latest expansion called Path of Fire.
To make this purchase easier you can use a coupon code released by ArenaNet to get a massive 50% off! You must purchase the game on the official store here.
The coupon code is: GW2WELCOMEBACK
There's a lot more information on the official news post for you to check out any particular content playthroughs on Twitch and links to the updated Wiki, you can check out the original news post here.