Change rear brakes. How do I do that?

Then it's best to leave it to a professional. There are a number of things we do to prevent noises and vibrations, and there's a lot of things do-it-yourselfers can accidentally do to cause those things. There's a whole lot more to a quality brake job than just hanging a few parts on the vehicle. There are also things you can do that will be discovered by a lawyer or insurance investigator when they're trying to shift the blame for a crash from their client who ran the red light, onto you.

If you really want to attempt this, start by visiting the library at a community college that offers an Automotive program. Look for a copy of a text book related to Brake Systems. You'll be amazed at what is involved, then, if you feel you want to tackle this, get a copy of the manufacturer's service manual and read through that section. When you're ready to start replacing parts, only take one side apart so you have the other side to look at for reference, and come back here to continue our conversation. I'll dig up a copy of a previous reply where I can share all kinds of tips and suggestions you won't find in any books.

Here is a article that may help. it may not be your truck but similar
https://www.2carpros.com/articles/how-to-replace-rear-brake-pads-and-rotors