How to get better at writing copy
Copy for an ad is the product of work by the art director and writer. The art director conceives the idea for the product and how to show it off and creates a visual presentation that reveals one or two key messages about the product.
Then, if you're running a print campaign, you have a typographer lay it out visually in a pleasing manner on the page. A good copywriter then translates those ideas into words that will be easy to read and remember, often packing more meaning into fewer words than would be possible otherwise in a tone that matches the image.