I bought a circular saw blade sharpener at yard sell the angle setting goes from 0 to 25 degrees how do I know what angle to set it at it does both steel an carbon tip blades chicago electric power tool model #96687

You match the tooth angles of the blade you are sharpening. See What you should know about circular saw blades for angle recommendations. Harbor Freight Tools sells this sharpener, you might be able to get a manual from them.