Choose Manage My Add-ins and select Upload My Add-in. For example take a look at the IF function in cell D2 below. First we will find the total marks using the SUM function in excel.
Therefore you wont find any of those functions in pre-dynamic Excel such as Excel 2019 Excel 2016 and lower.
Choose InsertModule in the editor. You have an empty code module sitting in front of you. Use this function to select one of up to 254 values based on the index number. Thats when the LOOKUP function can be useful.