1. boil fabric- natural fibres only! For example, pure undyed wool
2. prepare dye ingredients
3. boil ingredients in water
4. soak fabric in now coloured water from each pan
Probably the roughest guidelines I've ever written. It's a little more complicated, but that's the gist of it. There's some good info on dyestuffs here, but I have been a bit slapdash and used the classic strongly coloured plants and fruit, as I was purely experimenting and the fabric was not intended to be washed or worn.