If you have troubles finding the new code, Paul Thurrott has an exhaustive look into the process of securing the update.
The update brings new features and user interface tweaks to Microsoft’s smartphone platform. Chief among the new features is a broader rollout of Cortana, the voice-activated digital tool that Microsoft had previously only released in the United States.
The update also brings support for Live Folders, a feature that will allow Windows Phone users to better organize their main screens. Windows Phone is known for its ‘Live Tile’ interface that contains active squares which update to present new information. Update 1 improves the layout’s visual design.
The update is only available to Windows Phone 8.1 users for now. Expect Update 1 to become more generally available in time, and quickly. I’d hazard a guess that most Windows Phones will run the update by the end of the year.
As an aside, according to NeoWin, there are two updates going out, the first as preparation for Update 1 itself. As such, making the jump might take a moment longer than you would expect. Enjoy!