how do I download songs that are in the iCloud into my library

Click the iCloud download icon in iTunes.

And where is that button at? I have the same problem and I can't find it.

If you don't have iTunes Match, see http://support.apple.com/kb/ht2519. If you do have iTunes Match, the download icon (cloud with downward facing arrow) is to the right of any song that is in your iTunes Match library but has not yet been downloaded to your device or computer.