The first page of the wizard enables you to select the source and target object types. Which object type is the source and which is the target is not important at this stage. You may approach the selection as if you were simply selecting two object types to be linked together (i.e. to participate in the relation).

The 1st page of the Relation Wizard.

If you are creating an m:n or a time-related relation, a new link object type will be created for you so you don't have to worry about it now.

Click 'Next' to proceed to the 2nd page.