There are quite a few circuits and great LED tutorials on Instructables. Just check out some resources to get your bearings.
LED for beginners: www.instructables.com/id/LEDs-for-Beginners/
try out different circuits... blinking, back light, combinations =>
As the front wheel turns it creates alternating current (AC) power. The 'bridge' is a rectifier that converts the AC dynamo power to DC power. The bridge is made up of qty(4) 1N5818 diodes.
Bike Light Encapsulated in Epoxy
The battery pack absorbs any power not consumed by the USB device.
qty(4) 1N5818 Diodes
qty(8) White LEDs
qty(1) Battery Pack