To help the alignment, there is an arrow and the text North on the bottom of the transmitter. Align the transmitter so that the arrow points North.
Wind direction can be referred either to true North, which uses the Earth’s geographic meridians, or to the magnetic North, which is read with a magnetic compass. The magnetic declination is the difference in degrees between the true North and magnetic North. The source for the magnetic declination should be current as the declination changes over time.