Determine the angle or value you need to use
Make sure the angle is in the correct unit, usually degrees or radians
Use a scientific calculator and press the sin button
Enter the angle value
Press equals to get the result
If calculating manually, use the sine ratio in a right triangle: opposite side divided by hypotenuse
If using the unit circle, use the y-coordinate of the point on the circle
For a specific angle, use known sine values or trigonometric tables
For radians, use the same sine function with the radian value entered correctly