The Spotlight Icon, is found here, and looks like a magnifying glass:
You have two options to utilize this feature. Either move your mouse there, click, and begin typing, or use this short cut:
Command + space bar
The spotlight function will pop up right away and you can start typing. Once you type in the document name, use the arrow keys to navigate through the documents and once the one you want is selected, hit the "return" key to open it! If you use the shortcut and decide you don't want to be in Spotlight anymore, then hit "command + space bar" and it will disappear.
Easy as pie!