Try:
MyForm mf = new MyForm();
if (mf.ShowDialog() == DialogResult.OK)
{
...
}
But to be brutally honest, as Richard says, if you can't do that, you have an enormous amount to learn before you can even begin to start on this project.
You would be much, much better off getting a book on C# for Windows, and reading it first, doing each an every exercise as you go. I fear that you will end up missing far too much and the final product will be a horrible mess as a result.