Newbie Question: How to load Volumio on Pi with BerryBoot

I’m extremely new to working on installing distributions. I have a raspberry Pi 2 that I’m running OpenELEC, Debian Wheezy Rabian and RetroPie. I’d like to add the Volumio distribution to my boot list and keep the other distributions so that I can boot up my Raspberry Pi 2 and select which distribution to load.

However, I don’t see a way to load the Volumio distribution onto my Pi 2 through BerryBoot. I’m concerned that if I create a bootup flashcard with Volumio that I’ll wipe my other distributions during the process.

Can someone please help me as I’m not understanding what I need to do?

Thank you.