Do you mean that you've subscribed to iTunes Match, or that just your iTunes purchased music is available in the cloud ?
If iTunes Match then you should be able to download your music from the Match onto your iPad : iTunes Match on iPhone, iPad, or iPod touch
If you aren't using Match and it's your purchases are in the cloud then they should have a cloud against them in the Music app for downloading them, or you can download them via the Purchased tab in the iTunes store app. If you want to sync music from your computer's iTunes then connect the iPad to your computer and select it on the left-had sidebar of iTunes (option-command-S on a Mac, control-S if using the windows partition) and use the Music tab on the right-hand side of the iTunes screen to select and sync your music
Syncing media : http://support.apple.com/kb/HT1351