Q: como puedo actualizar mi ipos touch

Esta información puede ayudar a (This information can help you) Update the iOS software on your iPhone, iPad, or iPod touch - Apple Support

You have a 4G iPod touch since iOS 6.1.6 was not applicable to the 5 or 6G iPod touch.

The 4G iPod touch can't be updated beyond 6.1.6 since its hardware (only 256 MB of RAM is limiting).

However, you may be able to download/install the last version of an app that is compatible with 6.1.6

Starting when iOS 7 was released, Apple now allows downloading the last compatible version of some apps (iOS 4.2.1 and later only)

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

https://support.apple.com/en-us/HT201377

App Store: Downloading Older Versions of Apps

https://sites.google.com/site/appleclubfhs/support/advice-and-articles/app-store -downloading-older-versions-of-apps-ios

You first have to download the non-compatible version on your computer. Then when you try to purchase the version on your iPod you will be offered a compatible version if one exists.