To take part in the september challenge 2013 should I have signed-up somewhere or am I good to go as it is(without prior sign-up) and if I am able to participate where can I see my rating?
All you need to take part in any contest hosted by Codechef (either Long Contest or Short Contest format) is to have an account created, which is something you can do at any given time!
So, yes, you can still attend the contest and solve the problems
To see your rating, once you are logged in on Codechef main page, you can click on your chosen username on top right corner on screen and you will be able to see your rating there
Best of luck,
Just a note - if he asked question here, he has an account already…
there are two ratings 1.) global calculated after the contest (sometimes few day after) 2.) contest rating, you can see it in the table on the right or by using my extension