Q: on ipod 1st generation how do i download ios 1.1.5

Minecraft will not run on a first-generation iPod touch. You need at least a 3rd-gen model to run the required minimum version, iOS 5.0. You would not be able to get any additional games at all with iOS 1.x. You will need iOS 3.1.3. I don't know if it's still available, but take a look here:

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

Regards.

Minecraft requirements:

Compatibility: Requires iOS 5.0 or later. Compatible with iPhone, iPad, and iPod touch. This app is optimized for iPhone 5.

It will not run on a first generation iPod touch.

Minecraft is a game that requires iOS 5 and tyour iPod can only have iOS 3.1.3 which you will be able to download onto your iPod from iTunes.