LaCie Setup

Hello,

I needed to backup my mac and purchased a LaCie Slim Drive P'9223. During the initial setup, it was formatting my disk and a warning came on saying all contents on my disk will be deleted. I panicked and disconnect LaCie from my mac. Now I'm trying the setup again, and the setup assistant doesn't show up anymore. How can I get this thing installed and backup my computer? Please help. Thank you.