I know that many of you use these features all the time, but I also know that many are confused as to how to do so. This is a quick explanation that I hope helps. If anyone has additional info, please feel free to add.
Modify Profile:-  Login - On the upper right-hand side of the screen is Login : Register
 -  Now on the right-hand side you will see - 
Logged in as: {username}
Modify : Submit : Logout : upgrade -  Click Modify and complete the info.
 
Edit Submission(s):-  Login - see above instructions.
 -  Click {username}
 -  Now you will see your profile.
 -  Toward the bottom of the page you will see your submissions.
 -  Next to your submissions you will see an EDIT and possibly a DELETE button.
 -  Click 'EDIT' to change the details of a submission or
 -  Click 'DELETE' to remove the submission. (Note: this only available to Paid members or for songs that have been submitted for more than 5 days. Also, this will delete all comments/replies)
 
That's it!
I hope this helps.