Here is a quick way to change the permissions on all your Flickr photos:
Open the Flickr Organizr.
At the bottom, click Select all to choose all your photos. All the photos in the photostrip at the bottom will be marked in red outline now.
Drag any of the bottom photos to the work area in the middle. All the photos will be added to this area now.
At the top, click Permissions and choose Who can see, comment, tag? In the dialog that pops up, choose the permission you want applied on the photos.