Hi,
Thanks for the information. 
You will need a 10K resistor between pin8 and Uno gnd, so that pin 8 has 5v or gnd potential on it.
If you don't have a 10K pull down resistor, when your switch is open then pin8 will probably stay at the 5V potential, instead of going LOW to gnd.
Can I suggest you just write some code to turn your LED on and off as you activate the switch?
This will prove your circuit before getting into timing for the response to the button.
Thanks.. Tom.. 
