I would like to update Ipod 4th Generation

I don't understand the question.

If your iPod Touch 4 is already running iOS 6.1.2., then it is running the highest iOS version that iPod Touch model can run and be upgraded/updated to.

It can't be upgraded/updated any further.

Hi,

If you would like to update your iPod Touch, the following article will guide you on how to do so:

https://support.apple.com/en-gb/HT204204

Jack.