Adding additional photos to existing slide show

I'm sure this is probably a duh question, but I can't figure it out. I have created a slide show; including editing the photos and adding music - however, this is an ongoing project. Each time the group meets, I'm constantly needing to add new pictures to the show. After I add pictures I can then adjust the music or add more music depending on where I am on the project.

I can add pics to the project - but not the actual slide show without restarting the settings all over again. (like spacing and music).

Any help would be appreciated!!! 🙂