How to use the pen tool in Adobe Illustrator to draw a curved line
To draw a curved line, click and drag the mouse. That will establish the anchor point and the direction of the vector. The anchor point is indicated by a square. The vector is indicated by a line with two little dots on the end. Those are the handles that allow you to adjust the direction of the vector, and the angle of the curve. When you click elsewhere on the page, you will have a curved line.
Drawing and adjusting curved lines in Adobe Illustrator requires knowledge of anchor points, the selection tool, and the direct-select tool. If you don't understand those concepts, stop. Go back and become comfortable with them. This is because no one, not even someone like me who has been using this software since the 1980s, can draw a curved line without making some adjustments. The adjustments are done by changing the position of the anchor point and the direction and length of the handles.
My experience as a teacher and a trainer is that doing this is a "light bulb" moment for my students. After saying, "I'll never get this" several times, a light bulb goes off, and they get it. You will too. The more I explain it, the more complicated it seems. Let your fingers do it, when it clicks with you, it will be a pleasure. Learning it from a book or a video is almost impossible. Have someone show you. If it's in the budget, hire me. You will be pleasantly surprised.
Posted by Brad Hall