Ok, so you get your kool aid (I get mine from www.koolaiduk.com but there are other suppliers) and carefully rip the packet open. DO NOT INHALE THE POWDER.
Get some tupperware or something like that and mix the powder with about half a cup of water. For my yarn used about half the packet but could have used less - depends how much you want to dye.
Put your yarn into a skein and secure it in a couple of places so it doesn't tangle. You can only use animal fibres - cotton won't work.
If you are going for variegated then put a different colour in two different bowls with the water and plonk the skein in on top with half in one bowl and half in the other. Add some more water until the yarn is just covered. Squash it about a bit to let the dye penetrate. Then just walk off and leave it for an hour and open all the windows because by now your house will smell like strawberry shortcake's pants.
Make sure all the yarn has been covered and then lift it out of the tupperware and squeeze the excess liquid out of each colour. Get a piece of clingfil and lay the yarn on that. Remember not to agitate it too much if you're using wool as it might felt. Wrap the yarn loosely in the clingfilm.
Set up a steamer on the stove top and lay the clingfilm wrapped yarn in there. Put a lid on it and go away for another 30 minutes. Take the wrapped yarn out of the steamer and leave it to cool down completely. Carefully unwrap and carefully rinse any excess kool aid out using a sink of water. Leave to drip dry and when it is (dry) knit with it!
I have yet to discover how colourfast it is!