People who get good at drawing (or anything else) spend a lot of time drawing—like ten thousand hours. So if you want to learn to draw—draw a lot. If you’d like to start with simple drawings, Ed Emberley books help you use basic shapes for drawing funny animals in a simple cartoon style.
You can find guides for drawing more refined horses on YouTube, by entering the search term, “how to draw a horse step by step” in the empty box at the top of the web site. Then you can tell which videos people like the most by looking at how many times people watched them.