I dont know how to build in a button
Leave the buttons sewn onto the shirt. They won't work worth a damned with the Arduino. Use a switch, instead.
What do you suppose the digitalRead() function does?
which I can use to change the speed of the fade.
HOW do you want to use the fact that a switch is, or is not, pressed, to change the speed of the fade? Each time the switch is noticed to be pressed, the speed should randomly go up or down some amount between 0 and 4567237278452158?
I also need to make the fade go away
What the heck does that mean?