How do I say in Russian ''I wish you have fun''

There are a couple ways to express this in Russian. If you are addressing your friend or family member, which is an informal way of communication, you can say:

Желаю тебе приятно провести время! or
Повеселись! or
Желаю тебе весело провести время!

If you are addressing your boss or the person much older than you are as well as addressing multiple people at the same time, you need to be formal and can say:

Желаю вам приятно провести время!

Here is the recording teaching you to pronounce all above mentioned phrases http://www.box.net/shared/b06yct5djp You can either listen to it or download it onto your computer/ipod/mp3 player and practice.

Best of luck!