The following applys only to those who are using a Custom Domain name:
If you purchased a domain, and parked it on smf for free, you need to change the IP for the nameservers.
You would do that at your domain host (where you purchased the domain name and did the nameserver information originally.
Do NOT update the nameserver IP until you are given notice to do so when the move is completed. ..
THere will be a notice on the page when the move is completed telling you when it is okay to do so
Thanks,
SMF For Free