It's fairly easy, actually. http://www.livejournal.com/tools/memories....&filter=all
If you know anything about putting together code (or copying and pasting, rather) this should be alright.
Try any of those tutorials, and if it still doesn't help, feel free to post another topic, but make sure you read the top of the forum and make sure you give us enough information to help you out!
This will be closed and moved to the Resolved Topics forum - as I said before, please post a new one if you need help!