This document explains how to configure the Update a Business Object step in the WiscIT One-Step Editor
The "Update a Business Object" step will modify the fields of the business object that is within your current scope. For example, if the one-step was run on an incident, it would modify the fields of that incident unless the scope was changed at some point in the one-step.
When used in conjunction with logical steps (e.g. Decide Between Cases), it can be a powerful tool to update an object conditionally.