C# :: How To Add A Button To A Groupbox

I have a winform that I added a button to at design time.

Then I decided to add a groupbox to the form because I want to add a few more components to the gbox.

I notice if I add a gbox at design time and add components onto the gbox at design time, then the components show up when I run my app.

However, if I add a gbox after my form already has compoents on it, I can't see some of my components.

How do I move an existing button onto a new gbox so it shows?

I thought this would work but it doesn't:

gboxSettings.Controls.Add(btnChecklistFonts);