Adjust the 470k resistor to speed or slow down the blinking, or to slow the blinking you can increase size of the capacitor.
This is based on a 2V 20ma rated LED. The 400ohm resistor in front of the LED drives the LED just below max current rating at a conservative 14.4ma. Lower the 400ohm resistor to increase the milliamps, just keep in mind the current rating of the LED you are using and don't exceed the current it's rated at.
