You most likely have not turned on the tcp/ip protocol in the SQL service. Also make sure that your router and local workstations have opened port 1433 thru the firewall. This of course would include the sql server.
My .02
Don't open 1433 and expose the sql server to the net. There are way to many computers attacking port 1433. Use VPN.
John
John Fabiani
Woodland, CA