Go into itunes on the computer. Then, using which ever Apple ID the iPod is connected to, download the apps you want (on your computer itunes). Then go into your iPod, find the app in the app store and tap on the download button. If the app was made pre iOS 7 a pop up should say something like "This app version is not compatible with your device. Would you like to download a previous version?" Select yes and the app will download to the last supported version.