If you didn't enter the challenge, you may want to leave a link to your work as it is so hard to find on the site without a link. Also check out the Critique Circle. You won't get a lot of feedback, but it's a great place to get some.
The challenge is definitely the best place to get feedback. Once the judging is complete, usually over the weekend, Deb (the challenge director) will give an all-clear and you can throw a brick, which basically means you can leave a direct link to your story. Even if you didn't enter the challenge, but submitted your Black Sheep story under general submissions, you can still toss a brick and ask for feedback. Here is the brick link: viewforum.php?f=56
If you're new to FW, I also would really encourage you to check out Jan's thread. She is a seasoned writer and an experienced writer and gives generously of her time. The lessons on her thread are invaluable to beginner writers and Master writers. viewforum.php?f=67