Quick navigation is essential to getting proficient in Illustrator. The Hand tool and Zoom tool are keys to that navigation, and there are a few trick to use them efficiently. Scroll bars take too long to navigate and I never use them. I like these shortcuts instead.
Hand Tool
Find the Hand tool in the toolbar or use H as a shortcut.
Click anywhere on the document to grab and move the window around.
Hold the Space Bar. This will activate the Hand tool. Let go and you are back to the last tool you were using. Note: If you try that when you are typing, you’ll get spaces! In this case there is a shortcut to the shortcut: ⎇/Alt will show the Hand tool when you are in type editing.
Zoom Tool
Find the Zoom tool in the toolbar or use Z as a shortcut.
Click anywhere on the document to zoom in. No mystery there.
With Animated Zoom turned off in Preferences (Preferences > Performance > Uncheck Animated Zoom) you can click and drag the Zoom tool over any object and the area you define will zoom full screen and be centered in the window.
Everything is big. Now what? Double-click on the Hand tool to fit the artboard to the window, or double-click on the Zoom tool to show the artboard as actual size. You can also use the Zoom In and Out commands under the View menu: ⎇ (Mac)/Alt (PC), ⌘ (Mac)/Ctrl (PC).