I want to switch on a Led, my Voltage for switching is 3.3V.
Here is my Circuit, does it look alright?
Greetings Marius
yes it's ok 
it's a "common emitter" wiring
R1 can be more standard value 1K and R2 more standard 100 ohms
giving ((5-0.5)-3.2)/100 = 13mA to the led or R2=68 ohms if you want near 20mA
the ground must be common to the arduino board.
Thank you very much!
Yes, it will work fine. You could however increase the base resistor to about 2200 ohms as you will only need 2 mA to go well into saturation.
Russell.
the base resistor can be increased up to 10K without problem. but if the control source current (battery powered) is important. the best is to use Nmosfet instead of bipolar transistor like 2N7002