How to vary DC (0-450mA) current using Arduino output voltage(0-5 v DC)?
As this is roughly linear, you would use an LED Driver with an enable and/or PWM pin. Use PWM on the output pin of your Arduino. At 100% PWM, the full current will be seen 100% of the time. At 50%, the average current seen in the time period will be 50% of the full current. I.E. 450mA for 1/2 second and 0mA for 1/2 second is 225mA over 1 second average.

As LED lighting is not linear though, you will not see the LED at 50% brightness. We perceive brightness Logarithmically. Adjust your PWM as you see best.