- First you need to authorize your computer in iTunes, if you haven't already.
- Store > Authorize Computer
- Note: If you have already reached your 5 computer limit call iTunes Customer support to get your computer authorized on your account.
- Next, check for available downloads
- Store > Check For Available Downloads
iTunes will then check for what apps you have purchased before, and will give you an option to re-download your purchased apps or it will just show you all Apps and show updates that you need to download which essentially seems to re-download all the Apps with the latest versions available.