I install frei chat on JOomla and install module, but when i publish module its always blank, not chat windown nothing.

Try changing to different module positions.

And make sure that the module position is visible in the current template.

Also check if you can see the word freichat I'm your website source code.
If you can't see then it's module configuration issue, but if you can see it in the source but not in your website then there is some problem with freichat.