How do you create a virtual PS1 memory card?

I have the old 80 gig PS3 that's backwards compatible with PS1/PS2 games. I just got the MGS Essential Collection and am playing through MGS1. However, when I tried to save, the game told me I didn't have a memory card inserted. I've played tons of PS2 games on my PS3, and forget how I created a virtual memory card for the PS2. So, can somebody tell me how to create a memory card so that I can save my MGS1 data?

Thanks a ton.