What program are you talking about?
Once you know that, try googling <program name> toolbar add to see if it can find instructions. in MS Word, for example, the choices you get if you right click on an icon in either the tool bar or the quick start bar above that should do the trick.
My "Save' icon disappeared from the bar. I can still save via FILE & SAVE, but the icon is handier while I'm writing. Thanks guys.