Right-click on the Circle name in the Feature Tree, or select the Circle and then right-click. In the popup menu that appears, select either Edit Feature or Edit Sketch / Composite.
The Feature Guide will appear, automatically open to Required Step 1. You now return to the same situation in which you created the Composite Curve.
Make modifications in the current step, and / or click the icon for
Optional Step 1 and make modifications
in that step. Press OK 
or Apply 
in the Feature Guide to complete the function.
Note: If your changes result in a geometric impossibility, or cause problems in subsequent features, you will be warned by the Conflict Solver.
See also: