If you want to share a quiz with your friend all you need to do is generate the finished quiz (press the 'generate' button at the bottom right of the screen when you are entering questions). This will generate the finished .swf file that you can save or e-mail directly to whoever you wish to.
The .txt file is just a standard .txt file with the quiz data stored on it. The ContentGenerator.net programs load and use the data. You could send your friend the .txt file, get them to download and install the software and generate the .swf themselves. Yet this would be more if you'd want to let them edit or develop their own questions.
I think you just want to send them a quiz - in this case, just generate the quiz and send them the .swf file. Simple!
When you are using the multi-choice generator you get to the 'Enter questions' page. When you have entered all your questions, select the 'Generate' button at the bottom right:

Complete the quiz options and select the 'Generate' button again:

You should then generate a .swf and an .html file. Send the .swf file to your friend and they will be able to play the game. You can also upload the .swf file to the internet, share it via a USB drive or any other method.