Resistor with value closest to the calculated resistance value and watt value can be used.
For example; If the result is calculated as 1.7w, the closest upper value, the 2w resistor, would be appropriate.
The Led diodes has a current that it can safely handle. Going beyond that maximum current, even briefly, will damage the LED. Thus, limiting the current through the LED with the use of a series resistor is a common and simple practice.
This calculator will help you determine the value of the resistor to add in series with the LEDs to limit the current.
An LED has an anode (positive) lead and a cathode (negative ) lead.
The longer lead of an LED is the positive (anode) lead, while the shorter one is the negative (cathode).