Hi Woodelf, I don't know how well any of this will translate for the unsighted but here goes,
Go to www.apple.com/itunes/download this will allow you to download the latest version of itunes for your computer (it automatically detects your operating system)
Install the software
Once installed you need to create an account with Apple to allow you to purchase music, you should be able to do this by selecting store from the top menu and following the prompts. You will need to attach a credit card to the account and this is how you pay for things.
Once you have done that you can purchase your music via the itunes store and they will download to your computer.
Once on your computer you can listen to them from there or create an audio cd. To create a cd you select the tracks you want and right click, one of the options should be create an audio cd (or something similar), select the option, put a blank cd in your cd burner and you should be good to go, this is known as burning a cd by the way.
You can also load your current cds into itunes (this is known as ripping), if you load an audio cd when itunes is running it should automatically detect it and ask if you wish to import it, it is important whilst doing this that you are connected to the internet so that itunes can match your cd against a database to identify it and name the tracks correctly (downloaded music will already have this information).
You could then create new cds by selecting tracks from multiple albums and then burning those.
Whilst taking a look for a guide for blind people to use itunes I came across the following
http://www.blindtunes.net/ it seems to be some code written by a blind guy in the States to make using itunes easier or better for the blind, I have no association with him and no idea if it's any good.
Anything else I'll try to help but I'm assuming you use Windows and I use a Mac so there may be differences.
You should also be able to import downloaded music from other sources (Amazon for instance) into itunes and burn cds in the same way but I can't vouch for that as I've never done it.
Good luck
Ian