Instances can be added at the bottom of the General Information sub tab within the form.
You can name different uses of the same form separately, so that you can keep track of them. An instance title will concatenate with the form name in the convention of Form Name: Instance Title (ex: Self-Dispositions Assessment: Internship I). Thus, when selecting the Assessment Tool when creating an Assignment Template, you will see the name of the instance as a second component as part of the name.
Using instances will allow you to compare/contrast data for these two type of assessments. You will be able to run reports that can either combine or separate data collected for the different instances.