IPhone activation without a sim card?

I want to use my iPhone as an ipod. I recently enabled it because it was disabled. Now i'm setting it up again and I need a sim card. I don't have one and I can't use another one. How can I "hack" this page (below) IPhone activation without a sim card

I think you kind of have to use another sim card, whether the sim card works or doesn't just insert any simple sim card, and once it's activated you can take it out.