Shooting in Little Square

Hi, im a total noob in scriptin an i want to make a little first person space shooter but actually i dont know how to make my spaceship shoot. I want a little square on the screen where i can move my mouse und make a left klick for normal shoots and right klick for missiles (both without ammo but missiles with cooldown). And please write how i have to add it in my game, all i know i figured out by trying or with other with the help from other posts.

Watch this tutorial series - Good stuff.