C# Are we able to control which line to write in richtextbox?

C# Are we able to control which line to write in richtextbox?

I want to copy the text I type in a textbox to a richtextbox. It will
automatically appear in richtextbox while I type in the textbox. I do
something like below:
private void textBox1_TextChanged(object sender, EventArgs e)
{
richTextBox1.Text = textBox1.Text;
richTextBox1.Font = new Font("Comic Sans MS", 14);
}
But when we use richtextbox, the text will always begin to appear on the
first line on top left side. Let say I want the textbox's text to appear
in the 3rd line of the richtextbox. How do we do it?