Change names of columns in a template

[rdpar80]

I'm using xl 2016. I'm using the "expense report " template. I have renamed some columns but when I highlight those columns. a little box box says "enter (original name) expenses in this column under this(new name) heading.  HOw can I change the original name to the new name?

[#2]

Try selecting the cell, then go to Data, Data Validation.

[#3]

Oops, hit Post too soon; in data validation, go to the Input Message tab.

[#4]

Thanks ,,,got it::)