Install bittorrent, and find the Preferences screen. Then locate the download tab, and change the "Default download location" to wherever you want the MP3 to be put on your computer.
Go to a website such as www.torrentz.eu Search for whatever you want.
Before you are several options, some more gibberishy than others.
Consider these numbers on the right side of the screen.
You want the green ones to be high, and the blue ones to be low. Weigh that against how coherent the link description is, and how likely you will end up with exactly what you want.
Click on the file you want, and you will see a screen not unlike the one below. This is a list of all the websites that host the file you are trying to download. You will, in time, remember specific ones you enjoy for very petty but detailed reasons.
There are often ads for bizarre pornography on these websites. Get used to that. It is unescapable in this world.
After you choose a specific site, and click on the link, you will be taken to the screen on that website that has the torrent you are going to download. Always click on the "Download Torrent" button. Be careful though, lots of ads that lead you to shady websites disguise their buttons to trick you into clicking on them. Which is a very surreal thing when you get to thinking about it at 3:55 in the morning.
Here are three real buttons off three different sites:
Clicking that should download a teeny tiny file (it should only be downloading for a third of a second). Go find the torrent file in your computer, and double-click on it.
Assuming you have Bittorrent installed, it should open up automatically, having been summoned by the torrent file.
You let that download, and when it is done the screen will look like this:
It is part of this culture to let people "seed" the file that you just downloaded, so they may have it also. But the problem is that this is the fastest way for Comcast to send you a letter saying you've been caught downloading. And it's how citizens get sued. So once you see the new screen with the words "Seeding" replacing "Downloading" under the Status label, you can just click on it, and hit delete.
Then you go to wherever you had Bittorent download the MP3 to, and it will be there waiting for you.
WE DID IT!