Q: How do I download app on iPad1' 5.1.1

Applications which are compatible with iOS 5.1.1 can be downloaded or synced normally. For ones which are listed as requiring a newer iOS version, download them to a computer or compatible iOS device, click here, and try following the instructions.

That device can't be updated past 5.1.1.

(132932)

ipad 1 does not support higher ios than 5.1.1

to install older versions of an app if they exist

Install the latest compatible version of an app on an earlier version of iOS or OS X - Apple Support