How to format New Hard drive(2TB) installed in to mid2011 IMAC

Hello,

I have Mid2011 IMAC . My hard drive Crashed last month. I went to Micro Center and bought me a 2TB hard drive.

Pop open the IMAC. Replaced new Hard drive. Forgot to Format it. When I turn on the IMAC the Chime goes on screen comes on Flashing folder and question mark. So I popped in my original OS CD. It looks like it is reading something indicating by the hour glass (little spinning wheel). but then two minutes later the IMAC goes Dark Screen. Not able to see anything.

Is this happening because I did not format the Harddrive?

Or. I forgot to do something when I replaced the new Harddrive?

Please advice

thank you