Before you can digitize a new feature you have to add the Editor toolbar and start editing.

If you only have one workspace on your map, you can start editing the map layers at this point. In this example two workspaces are represented on the map, so you will need to choose the workspace you want to edit.

In this example you will see how to digitize a polygon to encompass a study area defined by the index grid lines located in an existing database. The index grid represents logical divisions within the data.

To create the new polygon, you will heads-up digitize against the index grid, snapping the vertices of your new polygon to the vertices of the grid lines.