HoW do I update my iPod touch with iOS 4.1 to iOS 6

Depending on which model you have, see below.

http://support.apple.com/kb/HT4972

Then you follow the instructions outlined in the Apple article linked above.

To update

Connect the iPod to your computer and update via iTunes

iTunes 10 for Windows: Update and restore software on iPod, iPhone, or iPad

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)

A 2G to 4.2.1. Requires iTunes version 10.X. If a Mac it requires OSX 10.5.8 or later. With 1OSX 10.4.11 you can only go to iTunes 9.X which gets you as high as iOS 4.1

A 3G to 5.1.1 Requires iTunes version 10.5 or later

A 4G to 6 Requires iTunes version 10.7 or later. For a Mac, that requires a Mac with OSX 10.6.8 or later

Identifying iPod models