What you need:
Dandelions, lots of them. Choose the fattest stems possible.
What to do:
Look at the flower. It has a stem attached. Near the end without the flower, but not on the end, you will want to make a slit in the stem about 3/4" long. This is Flower 1.
For a necklace, put the Flower 1 through the stem of the last flower in the chain.