It is really good that you are asking for help, most new writers ignore or angrily refute criticism. I would suggest a few things:
1) Look at the Featured stories on the site and notice the things the authors of them did well.
2) Read articles in the Help and Info section and also (SELF-ADVERTISEMENT ALERT) my story games The Land of Bad Writing and HOW NOT TO WRITE - Pokemon Adventures - Chapter 1- Part I - Section A - The Beginning of the Start for a few things to avoid in writing.
3) Get a good proof reader, whether it's a parent, an English teacher or an experienced author on this site to co-author or proofread your story for errors.
4) Capitalize, check for grammar, punctuation and spelling errors, plan your story and characters, take your time in writing (a REALLY good story game takes around at least 1 month to write), don't publish in parts and go for longer stories over short quick stories (if you like writing in parts that's ok, just don't publish them and when you're finished mash all the parts together into one story and call them chapters).
5) Keep writing. The more you write the better you will get, it's the same with anything whether it's playing a sport, eating chilli or assassinating people for the CIA, the more you do the better you will get :) Don't be discouraged by criticism but be aware of it and try to pick out the parts that are most useful. Also I find reading a lot helps, especially if writing about real-world events like you are doing.