Full tutorial text
Please see github for the full tutorial: https://github.com/gfoot/sdcard6502/blob/master/README.md
It includes example code stepping through the process of getting the SD card initialized and reading data from it, with plenty of comments explaining what's going on. In addition the text documents explain how to wire the card up to your 6522, what you should expect from each of the examples, and how to fix some possible errors that might occur.
Here's a video showing a 6502 homebrew computer reading text, images, and code from a SD card: