As for how to draw them, a compass, protractor and straight edge is the general method.
As to how to use them, that's impossible. There is no such thing as a real alchemy circle. These were a creation exclusive to the Fullmetal Alchemist story, based off symbols found in books such as the Key of Solomon, which was one of the more popular grimoirs of the middle ages. Their usage in Fullmetal Alchemist was an imaginative combination of science and magic. While alchemy was indeed real, it did not exist in that sense. It was a science similar to modern chemistry, but with different ideals and goals.
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A compass
Use a compass.
You use a compass to draw an accurate circle.
draw 2 circles the same size
To create three different drawings showing a number of circles and triangles in which the ratio is 2:3 you can: Start with an equilateral triangle, draw a circle inside it, draw an equilateral triangle inside the circle, draw a circle in the triangle and then draw an equilateral tiangle in the smallest circle. Or, you could draw 3 triangles and 2 circles in a line. Or, you could draw 3 triangles on a line with 2 circles between them.