You are in the iPad forum, just so that you know, but the process is the same for the iPod Touch as it is for the iPad, or iPhone for that matter. You need to sync the apps to the Touch using iTunes on your computer.
Connect the iPod to your computer and launch iTunes - if it does not start on its own.
Click on the iPod name on the left side under the devices heading
Click on the Apps Tab at the top of the iTunes window on the right
Click on all of the apps in the Apps List that you want to sync to the device.
Click on the Sync Apps Heading.
Click on Apply in the lower right corner of iTunes
Those same steps are used to sync any content to your iPod Touch from your iTunes library.