SQL inside firewall/Web Outside

You need to forward the router/firewall to the pc with SQL installed.
Something like:
Inbound Port     Type         PrivateIP            Private Port
1433                 TCP         192.168.1.213   1433

It all depends on the type of router you have but should lead you in the right direction.

if the SQL server is sitting inside a firewall and has a "non public" IP address.. ie/ 10.10.xx.xx , 192.168.xx.xx (some common ranges), and your Web server doesn't have an internal address like that, you wont be have one access the other

but i dunno, you dont provide enough info about the setup there... but typically a common setup is (this is going to be impossible to demonstrate in text, but i'll try anyways):

Outside World
       V
Router/FireWall
V                 V
Port 80         No access needed
V                 V
Web Srv        SQL srv

The web server should access the SQL server by the "internal" IP, and this protects people from the outside having ANY sort of direct access to the SQL box

IF the webserver is on the other side of the firewall (Outside World), not only do you have to open up port 1433 on the Firewall, you also need to tell (at the router/firewall) which internal IP "gets" this traffic