If you are using ADO.NET in your app.config (or web.config) you connection string should be something like the next one:
<setting name="ConnectionStrings" serializeas="String">
<value>server=192.168.1.2;database=YourDBName;user=sa;password=xxxxx;</value>
</setting>
More info about SQL Server connection strings are
here![
^]
Then by using MS SQL Server Management Studio, in the "Server Properties" -> Connections page you have to check "Allow remote connection to this server" option, and should work!