Data input/output in QT Creator (question)?

Question

C++ / C#

Hello everyone, I'm interested in how to fill out line edit forms, so that I can then send them to a regular text file by pressing the Save button ( push button ), and how else can I make a button to open the file and view it? Let's say I create a program "HR Department", go through authorization, then I press the button create a file and a new window opens (via messagebox) where I have a form to fill out (full name, position, etc.). Thanks in advance for the answers, but it seems to me that I will ask a couple of questions here as well. maybe I don't get it the first time. I couldn't find much information on YouTube.