To attach a Creative Commons license to your Flickr photo, go into the single photo, scroll down to Ower Seettings, click Edit, and then select the Creative Commons option from the "Set a license for this photo" pop-up menu. Read full insructions here, including how to set a default license for all of your photos.
Creative Commons licensed video by Flickr user Colleen Greene.
To attach a Creative Commons license (YouTube only supports basic Attribution CC BY) to your YouTube video, go into the "Edit" view, and then select the Creative Commons option from the "License and rights ownership" menu. This will indicate to others that they may remix your video by making the "Remix this video!" button visible underneath of your video player. Read full insructions here.
Creative Commons licensed video by Flickr user Colleen Greene.