To get the yarn ready to accept the Kool-Aid dye, you need to do a little preparation. As mentioned in step one, you'll want your yarn to be in the form of a hank tied loosely with acrylic yarn (which won't pick up the dye itself).
The yarn also needs to be completely wet and clean in order to take the dye uniformly. To make that happen, fill the sink with lukewarm water and a bit (maybe a teaspoon) of wool wash of plain old liquid dishwashing soap.
Allow the yarn to sit for at least half an hour, then drain the sink, rinse the yarn with the same temperature of water as it was soaking in, and press gently to ensure that all the soap is out of the fibers.