When researching the subject use the keyword persistence:
In computer science, persistence refers to the characteristic of state that outlives the process that created it.
So persistence has many forms: text files, XML, databases, shoot even memory outside the application fits this definition (its a little silly to store things in memory because a restart would destroy everything).
Assuming this is a winforms application then we are talking about driving the application with events. You can have a submit button which somebody clicks to perform a Save to the "persistence" thing you chose (usually a database).
private void Save(object sender, EventArgs args)
{
//Gather text info e.g.: var myText1 = myTextBox1.Text;
//Save to the database or wherever using Stream
//or SqlConnection or something else. See below
}
You could choose to save to the database with a SqlConnection or to a file with StreamWriter.