You will need:
Pliers
Faux flowers of your choice. $2 shops and spotlight stock them.
Head band
Floral tape (opt.)
Floral wire (you won't need this if your flowers are wired)
If your faux flowers are wired just coil each one around the headband in an arrangement of your choice. Trim stems with pliers if need be. If your flowers aren't wired, hold flower at the stem in desired position and begin wrapping the floral wire around both headband and flower.
Continue adding flowers until you get the desired look. The floral tape can be used to cover any 'mess' or sharp ends. Alternatively you could hot glue some felt on the inside to give a neat finish.