Port 1433 is probably behind a firewall, so you have to go into windows firewall > advanced to open the port by creating a new rule to open that port, Local Port > TCP 1433. But make sure, you set up a Scope (IP Range) on it at least if you do open it for security reasons, there are additional measures you can take as well to increase security. Only allow access to this port from people granted from YOUR ip address (www.whatismyip.com).
Make sure your ISP Router allows has this port open to the public and routed to the server with SQL on the router configurations.. If its a hosted site already, then nevermind that.. unless they have it blocked behind a firewall as well, which most usually dont'.
Once this is done, all you need to do is make sure your SQL server Main Instance Properties > Connections and say 'Allow remote Connections'
then you're set, you should be able to connect to the database, but using the credentials you should already have.. If you don't have the credentials, it's probably not a good idea for you to mess around creating a new user and mapping it to the proper db etc.. you may restrict access to your own website messing around here..
When connecting remotely, you just put in an ip address, and it usually asks you which db you want to connect to, the db's it allows you to with that users granted access.. You should have it from here..