You need the Fragments and Feedback forums. There are two, one for short stories and one for novels, where you can post up to thirteen lines of your stories, and solicit feedback on the full manuscript. Just DO NOT post the whole story. This is to protect your future publication rights.
For more information on these forums, go here:
http://www.hatrack.com/forums/writers/forum/Forum6/HTML/000002.html
It would probably be a good idea for you to visit the forum called "Please Read Here First". You won't see any posts unless you select 'show all topics' from the drop-down menu on the top right of the page.
Good luck and again, welcome!
Critiques are easy to come by. Also be ready to do a return crit (I always offer one when I post my pieces).
But as stated already crits are not hard to come by here. There's enough of us that someone or three or if you join a group down below, even more, will give you some advice. Some do a better job of that than others but we all say something helpful.
Of course, I rarely post because I have so little to post...and I rarely comment 'cause I don't want to while not posting myself. But I read a fair amount of it, and learn things from the comments...