Make the dye.
Prepare two pots of boiling water. Cut up the beets and place in one pot, allowing them to boil for one hour. Add a splash of the vinegar. This will help your dye hold pigment.
Pour the turmeric into the second pot and boil for eight minutes.
When both dyes are done, pour them into two bowls (or similar large containers).
Fold your shirt.
Lay the shirt on a flat surface.
Pinch the fabric between the neck and shoulder seam of the T-shirt. Carefully drag it toward the middle of the shirt, creating a vertical fold down the centerline of the shirt. Fold the sleeve inward, too, aligning its edge with the far end of the fold that you just made.
Repeat on the other side of the shirt. You should have one long column.