How do I delete photos from the photo library?

If you directly imported them (e.g., screen shots) to your iPod you can delete them from your iPod. If they were synced to the iPod yo have to unsync them.

The same way you got the there in the first place.

The sync process.

Remove the pic from the selected folder on your computer and sync.

Deselect the folder and sync.

Delete the photo from the computer and sync.

Any of these will work.