Q, I know how you feel. The first time I tried one I couldn't get anything out at all except squawks and air. Keep trying, you'll get it. Try having the call sitting roughly in the middle of your mouth. And then touch the tip of your tongue to the call as you force air between the call and your tongue. Once you get a consistent sound you can try moving your jaw as you call, and closing your lips at the end of the call. This can help make your calls sound more realistic.
Also, you might want to try trimming the tape all the way around the frame with scissors. They make the tape big enough to fit everyone, and it is too big for most people. Just take off about 1/16th of an inch and see how it fits. Don't take off too much at once, you can't put it back.
Good Luck!