I'm sure there is a simple answer

Hi,
I feel a bit embarrasses about asking this as I’m sure there is a simple answer. I’m just can’t find it.

I have just started with WordPress today and have on the menu Home and About. I cannot see how to add any other menu items. I have tried adding text and giving it a different category name but everything ends up in the about page.

How do I add another menu item? All help greatly appreciated.