I must be blind or something. I need to add tags to each picture - not album, necessarily. I don't seem to find a way to do this. Under the Tags tag, I see long lists of tags but how do I get them to relate to the images in question?

Or is that what Custom Data is all about?

Yes, you are half blind..;-) Visit the image subtab each album has on the backend and then click on the "show more fields" link. Then you will see the checkbox list to assign tags.

If you are logged in you can also add tags on the front end directly (in standard themes at least).

I hate when that happens. Thank you so much.