how can i make an led flashlight?

i dont no anything about making stuff with leds or anything about led projects, i got 100 assorted leds from a friend who moved, i would really like to make a flashlight with like 12 green or red leds but i dont no what kinda of resister i need or what kinda battery. im completely clueless about this stuff any help would be awesome!!!

Mdob7 years ago this site is very good at determining the correct resistor and array type.  For a 9V battery input "9" as your "source voltage".  If the LEDs are bright input "3" for the "diode forward voltage" if they are low power in- put "2.1" .  For the next box input "20".  Finally choose "12" as the number of LEDs in your array.  I hope that helped and I hope that you can read schematics.