Word 2013 or 2016 includes equations that you can drop into your documents—no formatting required. If the built-in equations don’t meet your needs, you can modify them or you can build your own sophisticated equation from scratch.
To insert a built-in equation, click Insert > Equation and choose the equation you want from the gallery.
If you’d rather start from scratch, type Alt+= or choose Insert New Equation at the bottom of the gallery.
After you insert the equation or the placeholder for your new equation, you’ll see Equation Tools for customizing and adding various elements to your equation.
To learn more about editing equations, see Change an equation.