Instructions are a bit lacking.

Nonetheless, I'm willing to bet that you were openning up the maze files into the Map Maker program, not into Amazeing X. Map Maker lets you make mazes, Amazeing X actually plays them. Just drag and drop the maze onto Amazeing X to open in there.

Once in that program, it should be obvious. You start off with Robby on the screen, the arrow keys move him around.

If you want a larger window to navigate the maze, then simply enlarge it. It's a standard macintosh window with the resize widget in the lower right of the window. Click and drag to make it bigger and fill up your whole screen, if you want.