When a point is required, the Assistance bar will display a message such as “Pick first point.” The coordinates for that point are shown in yellow in the dialog bar. The coordinates of that point are specified by either
Typing each coordinate using the keyboard. Use the TAB key to move to the next coordinate. This method is often used if you are entering exact coordinates off of a drawing.
Picking the point with the mouse in the graphics window. Use the appropriate snap mode to pick precise locations such as intersections or tangent points. This method is typically used when the point you want is relative to another piece of geometry.