If you have iPod 4G, and don't know how to install Google+ iOS App on your device, than this guide will help you to install it.
This procedure also works on Non-US devices too, it is also tested on Jailbroken iPod.
First you have to download iFunbox from HERE
And then, download *.ipa files from HERE
After the downloads complete, unzip the iFunbox.zip. Run iFunbox_en.exe
Select your device, then click Install App. Select the *.ipa file
That's it, your are done with installing Google+ iOS App on your iPod Touch 4G