You can auto-number headings in your ScreenSteps article. If you are not seeing the auto-number option, it might be because you have not selected a heading (you might have another type of content selected such as text, image, table, etc.).
Are you using the web or desktop editor?
Select a heading
You can select a heading by clicking on it either in the outline view, or in the main body of the article.
On the left-hand side of the editor is an outline view of your article.

Select a heading
You can select a heading by clicking on it either in the outline view, or in the main body of the article.
On the left-hand side of the desktop editor is an outline view of your article.

In the desktop editor you can set a preference that will automatically auto-number new headings. From the Preferences window, check the Auto-number new headings in articles checkbox.

The above procedure refers to old version of ScreenSteps. In the new version also, If we have an image between steps then the auto numbering gets messed up. How to automate even if an image exists?