The error message is pretty explicit:
Verify that the instance name is correct and that SQL Server is configured to allow remote connection.(Provider: SQL Network Interfaces, Error:52 - Unable to locate a Local Database Runtime installation. Verify that SQL Server Express is properly installed and that the Local Database Runtime feature is enabled.)
So start by looking at the connection string you are using, and verify that the server instance it refers to can be accessed from the PC you are running the code on.
Then check the login details in the string, and finally that the SQL server instance is configured for remote connections (many aren't for security reasons).
Sorry, but we can't do any of that for you: we can't access your connection string, or the SQL Server you are trying to use.