To insert command button:
View, Toolbars, Control Toolbox.
Choose the button tool and click and drag where you want it.
To add the code, double click the button you added, (then I had to cheat on this bit and google it as I couldn't recall) you put the following code in:
You may need to take it out of "Design" mode to test. Click the blue protractor icon on the control toolbar to do that.