Here are some videos that should help you understand the whistle register a little bit better. There is no quick answer to teaching yourself this technique but its been said that anyone can sing in this register with the correct training and commitment. Adam Lopez- yes it is possible for men to sing whistle notes- said that he taught himself how to sing in the whistle register by practising and building his range slowly over time. The most important thing to remember is if it hurts when you try than you must stop because you are doing it incorrectly.
Brett Manning vocal teacher to the stars shows you even a man can sing those high, whistle, notes. He even explains how he achieves them.