You can sync then to the iPod by:
Also, from Users Guide:
Use the Apps Pane to sync App Store apps, arrange apps on the iPod touch Home
screen, or copy documents between iPod touch and your computer.
Select “Automatically sync new apps” to sync new apps to iPod touch that you
downloaded or synced from another device. If you delete an app on iPod touch, you
can reinstall it from the Apps pane as long as it was previously synced.
You can create documents on iPod touch with apps that support file sharing, and then
copy those documents to your computer. You can also copy documents from your
computer to iPod touch, and use them with apps that support file sharing. See “File
Sharing” on page 51.
On he iPod you can also go to App app and purchase/download apps directly to the iPod.