Hi Brigitte!
I think you're going to love
Memory Maker! I've had a chance to try out the service myself and now I can't imagine visiting Walt Disney World without it. The fact that it's easy to use is one thing that makes it so fantastic.
Once you have your Memory Maker card, just use the card number (on the back) to link it to your My Disney Experience account using the "My Reservations" page. If you received an email with a confirmation number, you can also use that number to link it to your account.
During your vacation, photos can then be added to your account using your linked MagicBand, your Memory Maker card or a linked Disney PhotoPass card. In addition, you will be able to view and download photos added by those on your Family & Friends list in My Disney Experience, so they will also be able to use their own MagicBands to link photos to your Memory Maker account (or either of the other card options above).
I hope that helps, Brigitte, but if you have any other vacation planning questions, just stop back by the Disney Parks Moms Panel!
Beth