Look for a gear icon to access the Preferences.
 

Preferences - General

The General tab of the Elgato Stream Deck Preferences allows you to change the Device Name of your Stream Deck.  This can be useful if more than one Stream Deck is connected to your computer - that way you can more easily identify them.

You can also change the Brightness of keys, using a slider.

You can also see the Software Version, and use the Check For Updates... button to download newer software (if it exists at that moment).

The Firmware Version is also listed, if your device is attached.
 

 

Preferences - Account

The Account tab of the Elgato Stream Deck Preferences allows you to enter your account information for various services, including:

Twitter
Twitch.tv,
TipeeeStream

Once your account is authorized, you can do things like send out Tweets at the push of a button, interact with your Twitch audience, or access TipeeeStream's Scene Creator.
 

 

Preferences - Profiles

The Profiles tab of the Elgato Stream Deck Preferences is very important.  It lets you create profiles of keys that you can switch between.