First: enable SQL Server itself to be accessed over the network

1. Open SQL Server Configuration Manager
2. Expand SQL Server Network Configuration and click Protocols for MSSQLSERVER
3. Doubleclick TCP/IP
4. Set Enabled to Yes

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Secondly: change the Windows Firewall to allow incoming connections on the TCP port of SQL Server

1. Open Windows Firewall with Advanced Security
2. Click on New Rule

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Now in the wizard you set the type of the rule to Port.

Hit Next.

On the second window you set the Specific local ports to 1433:

Hit Next.

Allow the connection.

Hit Next.

Now enable the checkboxes you want to. I set mine only to Private. Because I only need to access the SQL on my laptop at home:

Hit Next.

Hit Finish and you’re ready to develop SQL over network