adding apps to 2nd generation apple tv

Withe the 3rd generation and earlier Apple TV, you can only update your software which will update the built-in apps. See the following from Download apps on your Apple TV - Apple Support

If you can't find the App Store

The App Store isn’t available on Apple TV (3rd generation). If you have this model, you can't download new apps, but you can update your software to update your built-in apps.

Unfortunately you can’t.

The 2nd Gen AppleTV has only “built in” apps.

I does not support the subsequently-added “App Store” model.