The ribbon is the horizontal menu between your document title and the document. There are multiple equations in the drop-down list then scroll down and select one of them to meet your actual needs. In its wisdom Word makes an educated guess about what you want the formula to do and places a formula in the Formula box.
On the Table Tools Layout tab click the Formula button.
Position the cursor where you want to insert the formula. Select the Insert tab on the ribbon. How to Insert Mathematical Formulas and Symbols in Word Method 1. Insert Math Equation 1.