adding child nodes in treeview

I'm new to C# and don't have any programming experience. But I've finish a C# basics. Now I would like to design a simple tree view by adding parent node and child node.

I would like to add a second child for the Second node, I'm quite stuck here and don't know what's next.

Any ideas?

Here is the code:

    private void addParentNode_Click(object sender, EventArgs e)
    {
        string yourParentNode;
        yourParentNode = textBox1.Text.Trim();
        treeView2.Nodes.Add(yourParentNode);
    }

    private void addChildNode_Click(object sender, EventArgs e)
    {
        string yourChildNode;
        yourChildNode = textBox1.Text.Trim();
        treeView2.Nodes[0].Nodes.Add(yourChildNode);
    }

Sorry I wasn't clear, I'm not sure if I really need this one here:

  //treeView1.BeginUpdate(); 
  //treeView1.Nodes.Clear();

What I'm trying to do, is to add Parent Nodes and child node. In my code, I can add several Parent Nodes, but if I want to add a child node, it only add in the first parent node. I want that if I add a child node, I want to add it to the second parent or third parent.

In my code I only use one treeview here which names as treeview2 Here is the screenshot

this is how my final code looks like: Before I put the else, I'm getting an error if I don't select anything. So I made it that way that if there is nothing selected it will add the "child node" to the "default node" or (parent1 node). It seems to work good. Thanks guys;-)

    //This is for adding a parent node
    private void addParentNode_Click(object sender, EventArgs e)
    {
        treeView2.BeginUpdate();

        string yourParentNode;
        yourParentNode = textBox1.Text.Trim();
        treeView2.Nodes.Add(yourParentNode);
        treeView2.EndUpdate();
    }

    //This is