Click in an empty paragraph.
Apply a paragraph style from the Paragraph Catalog, or set up your own format. The paragraph style determines the alignment, vertical spacing, and any autonumber for the paragraph that contains the equation.
Click the Equations button at the right side of the document window.
On the Equations panel, choose one of the New Equation commands from the Equations drop-down list. Small, Medium, and Large specify the font sizes used in the new equation.
A new equation object appears as a question mark in a frame anchored below the empty paragraph. The first math element you insert replaces the question mark prompt.
Insert the math elements in the equation by typing the elements or by clicking items on the Equations panel.
Choose Shrink-Wrap Equation from the Equations drop-down list. This option shrinks the frame around the equation and places the equation in the empty paragraph.