While the simplest and most direct method for editing xrefs is to open the source file for the referenced drawing, there is an alternative that can be more convenient.
If you need to edit the model space objects in an xref, you can access the xref or a nested xref directly from the Reference Manager or with the XOPEN command. Select the xref, and then using the shortcut menu in the Reference Manager, open the xref’s source file. After you save the edits, close the drawing. In your original drawing, click the Refresh Content button in the Reference Manager, and resume working.
Make sure you know whether the referenced drawing is also referenced by other drawings, and the the changes you make are appropriate in other instances.