InDesign users can move content between existing assignments as well as from the Unassigned InCopy Content section of the Assignments panel. You can also create a new assignment and move content to it.
Drag the content from one assignment to another.
To move content to an existing assignment, choose Add To Assignment from the Assignments panel menu, and then select the desired assignment.
To create a new assignment as you move content, from the Assignments panel menu, choose Add To Assignment > New, and then specify options in the New Assignment dialog box.