To Attach Multiple References from a Single Directory

In the References dialog ( Drawing > Attach > References dialog launcher ), click the Attach Reference icon.

The Attach Reference dialog opens.
Select the DGN files that contain the models to attach as references.
Tip: To select multiple files, hold the <Ctrl> or <Shift> key as you select the files.
From the Attachment Method option menu, select Interactive.
The Reference Attachment Properties dialog opens.
Click Open.
The Reference Attachment Properties dialog opens for the first file in the selection list.
Modify the attachment settings, as required, then click OK.
The Reference Attachment Properties dialog opens for the next file in the selection list.
Modify the attachment settings, as required, for each subsequent reference in the list.