I am not a Mac owner and am only helping a friend. He bought a new external HD and he wanted to backup all of his pictures (he uses iPhoto). So, I drag and dropped the Pictures folder onto the HD (formatted as HFS+). I'm assuming this also includes his iPhoto Library. I plan on option click open iPhotos and going into preferences to point to the external HD.
However, once I point to the new iPhoto location, what is the easiest way to delete all files within his Pictures folder? Right now he has 370 GB of pictures on his 500 GB MacBook Pro and so needs to make space badly. Also, once the Library is pointed to the external. He will always have to have it connected when trying to import new pictures into his computer correct?
I know this might seem like a simple question but google wasn't as helpful as I thought it would be.