You can find video instructions here:
http://screencast.com/t/xbHfCU8O0E0Here are the written instructions:
- Open one of your albums.
- Click the [Edit] link under the picture you want to copy
- Scroll down to the Additional Options section
- Click the [Copy item] link
- To copy the picture to a public album (like a swaps album) click the box next to Category
- Select the name of the album you want to copy your picture to.
- Click the Copy item button