How to install ios 7.1 if ios 7.1.1 is out?

Its for my iphone 4s

Apple ios can't downgrade system any ios version. You can upgrade latest version…

Download the update you want http://www.iclarified.com/entry/index.php?enid=750 it has to be your device. Open iTunes and navigate to your iPhone. You'll see the "Restore iPhone…" button. Hold shift and click on it. Navigate to your downloaded firmware. Disconnect from internet just in case so it won't tell that you have a newer version. I don't know if it's gonna work, but you have to try.

If you want iOS 7.1 get 7.1.1 while you can because it's the same just with some bug fixes. If you wait too long it'll be 7.2 soon and you can't downgrade.