How to add a custom column with the "IF" function?

I have two different columns of different tables, in table A I have the column Year_Rest and in table B I have the column Year_Empenho_Rest, and I'm creating a report that I need to have a custom column:

= If (Year_Rest> Year_Empenho_Rest, Year_Empenho_Rest)

I'm trying to add a polite column with this condition in one of the two tables, but I'm not getting it, what should I do?

Note: the two tables relate directly.