a) Make sure Remote connections are enabled on the SQL SERVER instance.
b) Configure your firewall to allow connections through the desired ports.
Default SQL SERVER instance uses port 1433 for TCP/IP
1. Open the Windows Firewall with Advanced Security
2. Right Click on inbound rules and select New Rule
3. Create a Port Rule, Click Next
4. Choose TCP rule and choose ports 1433, 1444. Click Next.
5. Choose Allow the connection. Click Next.
6. Choose the correct profile. By default all of them are on, but you might choose only to let domain machines access SQL... Click Next
7. Specify a Name and a Description for the Inbound Rule. Click Finish
8. Your rule should be created
Now use your client to connect to the Remote SQL SERVER instance and it will work.