Yo can just use Write Characters to File. Using this is really simple and I don't think an example is really necessary. Search the shipping examples if you really get stuck.
I posted the above link because these questions are extremely basic. You really need to take a LabVIEW course. For someone who has been posting questions since the one at http://forums.ni.com/ni/board/message?board.id=170&message.id=81055#M81055 for close to two years, I'm a little surprised you know so little.
This is a problem that you should be able to fix yourself at this point. I will give you a hint - look at the Boolean values that you have wired to the two write functions.
It works with option to add time-stamp in a data file. one thing that I find odd is that when 'append date info to file' in 'false' state. (replace existing prompt comes up twice...)