Q: Is it possible to update my itouch 8Gb to iOS 6.0 or later?if yes, how,?

You will need a 4th or 5th generation iPod Touch to update past iOS 5.

The iPod Touch 4G will run iOS6 and the iPod Touch 5G iOS7.

Connect to iTunes on your computer to update.

Only if your iPod has cameras, then it is a 4G and will go to iOS 6.1.5

Otherwise you either have:

- The original (1G) iPod

A 1G iPod can go to iOS 2.2 via iTunes and iOS 3.1.3 via

Purchasing iOS 3.1 Software Update for iPod touch (1st generation)       

https://buy.itunes.apple.com/WebObjects/MZFinance.woa/wa/touchLegacyLandingPage

- Or a 2G to 4.2.1. Requires iTunes version 1o or higher. If a Mac it requires OSX 10.5.8 or later.

- A 4G to 6.1.5  Requires iTunes version 10.7 or later. For a Mac, that requires a Mac with OSX 10.6.8 or later

Identifying iPod models

That means you either have a 1G that can go as high as 3.1.3 or a 2G that can go as high as 4.2.1.