When the game says "Press any key to start", press the "Spacebar". Use ARROW keys to move your character, space bar to use the sword. Read the sign posts along the way to learn the secrets of your realm. Kill the bad guys, use the good guys, find emeralds for power and life, pick up helpful things along the way. Click "Options" for more stuff.

HINT: You never know what you might find under a bush! Use the "A" key.
But most important, rescue Zelda! (Don't ask for help, your on your own here.)