Following the package instructions, mix the rit dye with hot water and a pinch of salt
I found it easier to hold the shirt if I put a spatula thorugh the arm holes.
Dip the tee in first as quickly as possible up a few inches below the armpits. Then dip again a few inches below that, holding it in the dye for about 5 seconds. Dip again, a few inches below that holding it in the dye for 10 seconds and so on. Leave the bottom portion in the dye for at least 5 minutes.
The colors should blend into each other as shown. When you dip and hold, be certain to not hold it in the exact same spot so a harsh line won't appear. Sway and bob it from side to side and up and down a bit so the colors blend into eachother.
The last portion can sit in the dye for as long as needed to produce the deep color you want. Mine sat for about 10 minutes.
Rinse the shirt out with cool water until the water runs clear and then toss into the washing machine and clean as normal.