sigh. ohms law is V = I*R. rearrange R = V/I = (5V-3.3V)/.02 = 85 next higher standard 5% value is 91. W = V * I = 1.7*.02 = .034 1/8 watt will do fine. However, you could probably use an 82 ohm resistor with no ill effects. This presumes you are using a 5V supply. If your supply is different, you will need to recalculate the numbers. Note that the LED "consumes" 3.3v so you only need the resistor for the remaining "unconsumed" voltage in order to set the current. (yes, I know this is imprecise but it makes it easier to explain)