As we're not sure what you have done exactly it's hard to be certain how to progress.
This is how you move an iPhoto Library
Make sure the drive is formatted Mac OS Extended (Journaled)
1. Quit iPhoto
2. Copy the iPhoto Library from your Pictures Folder to the External Disk.
3. Hold down the option (or alt) key while launching iPhoto. From the resulting menu select 'Choose Library' and navigate to the new location. From that point on this will be the default location of your library.
4. Test the library and when you're sure all is well, trash the one on your internal HD to free up space.
There is no way you've done that if you can no longer see the Library at Me/Pictures.
Yes, I've clearly done something wrong. I dragged the iPhoto library from Me/Pictures to my external hard drive. I could see the library on the external drive but not in Me/Pictures. I just tried dragging it back. So I now have three options when I press option/alt and launch iPhoto.
1) Users/Me/Movies/iMovie Projects.localized/iPhoto Library
2) Users/Me/Pictures/iPhoto Library
3) /Volumes/MyExternalDrive/iPhoto Library
The only one that works is #1. So the question now is: where did I go wrong and how do I correct it?
Yes, I can see all my pictures and folders if I launch iPhoto from Users/Me/iMovie Projects.localized/iPhoto Library.
Also, since I did the same action, dragging the icon over to the external drive and back, I now have iPhoto Library icons on the external drive and in Me/Pictures. What to do?
Feel like I've made a mess and haven't necessarily freed up any space on my MacBook.