First, let's have a look to the Configure menu. Select the difficulty of the game (Easy, Moderate or Hard). No surprise Hard mode is the fastest. From this menu you can also enable or disable sound effects, using the check box. Here we go now, playing with the mouse : right click to toss the clay pigeon into the air, then, aim the crosshairs and left click to fire at the target. A round ends after 25 targets.
Two last things: the registered version has no 'nag screens' ; running on recent computers, the game is way too fast, even in Easy mode. So consider using a slowdown utility.