How do I authorize this computer to add it (as I've removed the last one) to my cloud?

Wondering how to 'authorize' a new computer to add it to our cloud. I purchased new music and cannot get it onto my ipod shuffle. The message tells me that I can have 3 computers or 'products' authorized. I removed the computer that died that prompted this new one to come into our lives. Now, I cannot get this one, nor find the option to "Authorize" a new computer to transfer my most current iPod purchases. Any help?