Automatic Numbering

Choose a cell style such as DisplayFormulaNumbered.
Use Insert Automatic Numbering with a counter name such as Section.

Two ways to set up automatic numbering in a Wolfram System notebook.

Using the DisplayFormulaNumbered Style

These cells are in DisplayFormulaNumbered style. DisplayFormulaNumbered style is available in the default stylesheet.


Using the AutomaticNumbering Menu Item

The input for each cell here is exactly the same, but the cells contain an element that displays as a progressively larger number as one goes through the notebook.