Not to sure I never had a galaxy I've only had droids but on an android you can just hold the folder the pictures in or holds the picture itself for 2-3 seconds and the list should come up and renaming it should be one of the options if that's not it then call Samsung tech support or google it school gold the exact question you asked
The "album" name is the name of the folder the pictures are in - rename the folder (with a file manager app - My Files will do, just long-press the folder, then menu [left button next to Home], then rename).