I cant transfer my iTunes songs?

I'm trying to transfer the songs from my Ipod to my new computer's Itunes, when I clicked transfer songs, it said that some of the songs were not authorized to be transferred, it then asked me to if I wanted to authorize songs by signing in, I stupidly put in the wrong pword several times ( I haven't signed on in a while), it then asked me if I had forgotten my pword and I click no, and the window closed, now whenever I select transfer the window for the authorization wont open, how do I make this window open again?