If you wondering how to install ipa files on your ipod or iphone just follow the tutorial.
1. First of all, you will need to jailbreak your ipod or iphone. To do that follow the tutorial: jailbreaking-41-ipod-touch-2g
2. Next you need to update all files with Cydia which will appear on your ipod or iphone after you jailbreak it.
3. Next make sure you synchronize your ipod or iphone with your iTunes. Make sure you have at least one application which is not default one. Other wise application tab will not appear in your iTunes.
4. Open cydia.
5. Go to manage and add http://cydia.hackulo.us source ( Manage>Sources>Edit>Add
6. Search for "Appsync" application for current firmware and install it. ( Search>Appsync>Install>Confirm )
7. Than just download you needed one ipa file from internet.
8. Drag the ipa file to your iTunes application section.
9. Synchronize new content with your ipod or iphone.