There several ways that you can navigate with Explorer. All are explained in the Help, under Exploring and Navigating Maps.

One of the ways is using the Navigator, the round disk that by default resides in the lower left of the map display. When it's maximized you'll see tips that explain the various controls. The tips are useful, but you may want to toggle them off eventually. To do so, choose Tools > Options, then click Map Display. You'll see a checkbox for Show Tooltips, which is enabled by default. Just check it off.

Another way to navigate is using the mouse. Again, a good explanation is found in the Help. Try holding down the middle mouse button, and moving your mouse up to tilt your perpsective, then move your mouse to the right or left. That's an effective way to rotate your view, especially when zoomed in.

The keyboard is also very handy for navigation. Try hitting the F key to move forward, then use the Left and Right Arrow keys to change direction. Hit the Up Arrow to move faster, the Down Arrow will slow you down, or move you in the opposite direction. The J and L keys zoom you in and out respectively, the I and K keys adjust your tilt. 

You'll likely find that a combination of using all three navigation methods--mouse, keyboard, and Navigator--will suit your personal navigation needs. Just experiment to find the right combination for you.