The Address Bar is displayed across the top of the application window, below the toolbar. You can change the relative position of the address bar and toolbar by dragging the grip bar displayed on the left side of address bar.
To hide or display the Address Bar, choose Address Bar from the View menu (ALT, V, A).
Autocomplete feature provides list of existing subkeys and filters it out as you type more symbols of the path. To take advantage of autocomplete feature set the input focus to the address bar and begin typing.
For list of top-level keys begin starting with \\ (backslash) or with H if you are used to top-level names starting with HKEY_ prefix.
You can also use common abbreviations, like HKLM or HKCU. As soon as you type \\ (backslash) you will see the list of available subkeys.
Using the address bar instead of expanding the tree view gives you an option to have partially expanded tree view that is easier to see and navigate.
Use View Address Bar menu command to display and hide the Address Bar.