What is the first step to apply data validation rules for decimal numbers?

The initial step to apply data validation rules for decimal numbers involves selecting the Data tab and then clicking on Data Validation. This action directs you to the necessary tools specifically designed for setting validation criteria for cell entries.

When you open the Data tab, you gain access to the Data Validation feature, which allows you to define specific conditions that must be met for data to be entered into a cell. After clicking Data Validation, you can choose "Decimal" as the type of validation and set your parameters accordingly, such as specifying a range for acceptable decimal values.

Other options do not lead directly to data validation settings tailored for decimal numbers. The Formulas tab focuses on functions and calculation tools, while the Insert Function dialog is meant for inserting various formulas into cells. The Data Validation button mentioned as a standalone option overlooks the essential prerequisite of first navigating to the Data tab, which houses all relevant data management features. Thus, selecting the Data tab, followed by Data Validation, is indeed the correct and logical approach for applying data validation rules for decimal numbers.