Class joins may be used to enable reporting on data from multiple classes or tables. You can set this in the Data Access tab of the Report Definition. For each class join, define one or more logical conditions that specify how to match or join corresponding instances in different classes.
Please refer the following help document for detailed steps.
Joins are useful when we associate two different classes and present columns which belong to the class in the second class. For example, we use a predefined association between Assign-Worklist and the work class to display columns belonging to both these classes.
As your intention is just to display the properties from two different classes then you can use Class Joins.