If you have SQL Server authentication, you need to provide username and password in the Connection string. It will look different depending on which technology you use to connect. With .NET Framework Data Provider for SQL Server and Microsoft OLEDB Provider for SQL Server, it's "User ID=yourusername" and "Password=yourpassword". If you use SQL Native client OLEDB Provider or ODBC it's "uid=yourusername" and "pwd=yourpassword". On
https://www.connectionstrings.com/sql-server/ you can find a more or less complete list of Connection strings for connecting to SQL Server using different Technologies.