Q: How to update to an iOS 8.0

They didn't come out with iOS 8 yet but if you mean iOS 7, then you go to settings, under general, then click software update, then hit start update and it should start updating.

Hi Binversie,

As Bells0607 said Apple has not yet come out with iOS 8 and as you have iPod Touch with iOS 4 installed in it which means you have 2nd Generation of iPod Touch with you and I am sorry to say that iPod Touch 2nd Gen supports maximum of iOS 4.2.1 which cannot be Upgraded Further.

Hope this Answers to your Question

There is no iOS 8 yet.

To update

The Settings>General>Software Update comes with iOS 5 and later.

Connect the iPod to your computer and update via iTunes as far as your iPod model allows

iOS: How to update your iPhone, iPad, or iPod touch

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

- A 2G to 4.2.1. Requires iTunes version 10 or higher. If a Mac it requires OSX 10.5.8 or later.

- A 3G to 5.1.1  Requires iTunes version 10.5 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

- A 5G to iOS 7. Requires iTunes 11.1 or later if you update via iTunes

Identifying iPod models