To calculate the effect of temperature, you have to have a "baseline" temperature that you compare everything off of. For example, you might base everything from 75 degrees (F), so that you can calculate the effective playing distance of a shot in other conditions. E.g. "a 150 shot in 75F plays how far when it's 50F?"
In addition you can adjust for humidity and barometric pressure in the "advanced parameters" section. The baseline pressure is sea-level, which is 29.92". If you look up your current weather conditions you can find the current Temp, Humidity, and Pressure for your location. Pressure takes into account altitude
To calculate the effect of wind, enter the speed of the wind along with the wind direction relative to your shot. 0 (degrees) is a straight on head wind, 90 is wind from the right, 180 is downwind, and 270 is wind from the left. Of course you can enter any value from 0 to 359 degrees. If the wind is quartering into you, that is 45 degrees (just like on a compass).