Now that you've read our How to Use Our Comments and Not Get Banned guide--which is really very easy to follow--here's how to edit your comments.
Simply keep yourself logged in, scroll down to the Comments section and you should see a link called "Read the comments in the forums."
Click on that. You'll be taken to the forums page for the particular thread that you're on, and as long as you're signed in, you can edit your own comments.
Simply click on the editing button that appears in your post and you'll be able to edit.