Your music has been uploaded to iCloud using iTunes Match, right? To transfer it to your computer, open iTunes, enable iTunes Match with the AppleID you used to upload the music to iCloud.
Then download the songs:
- Select all songs with ⌘A or select only the tracks you want to download
- Click the download arrow to the right of the songs or right click on the selected items and click Download
To disable: use the "Store" menu: Turn off iTunes Match after you downloaded all songs.