A warm welcome to our newbies; come meet new and not-so-new members of Writing.Com!
Your best bet is put pen to paper or fingers to keyboard and start writing. Then go back later and see if you can make what you wrote better. Do that a few times, maybe a bunch of times. At some point see if you can get some feedback from other writers. Put your ego aside (this can be hard!), and pay attention if they tell you where you can improve. Review other people's works so you can learn more about spotting weak spots. Lather, rinse, repeat.
There are also courses here on WdC on all sorts of writing-related topics. Here's a link: "WDC Writers University" .
Good luck, and be brave! Post that first item in your port! If you need any help, don't hesitate to let me know. You might also consider stopping by "The Fox's Socks BIRTHDAY PARTYPALOOZA" to learn more about how WdC works.