if you don't know that, you should:
1. uninstall netbeans
2. learn the basics.
besides the fact that all use of netbeans changes here, is that you get generated crap that is called 'code' for some reason, which is pretty hard to read, let alone maintain (without introducing regression bugs).
from your post, I deduct you don't know how to use methods, nor the api/other documentation.
basic steps are:
read data from file
write text in JTextArea
and sure, you'll need to create subtasks there, but still.