How to edit sign up page with Anti Splog

I'm desperately trying to make some edits to my user sign up page on my multisite network. I've read that it is possible through Anti-splog plgin by copying wp-signup.php to the wp-content folder and then changing the name to custom-wpsignup.php. Apparently any changes to this new file will replace the current sign up page. I have done the above steps but I don't know the URL for my new signup page.