You can walk around Space by clicking the ground in front of you, using arrow keys or WASD.
You can fly by clicking F then use
E to hover up C to hover down
Or Page Up / Page Down
Then use arrow keys or WASD to fly around.
Hold your right mouse button down and move your mouse to look around. Use your mouse wheel to zoom.
Hold down SHIFT to run instead of walk when you use WASD or arrow keys. You will also fly faster if you hold down SHIFT.