Hello @Mark Welcome to the Microsoft Q&A and thank you for posting your questions here. You were asking on how to provide credential information to connect Link Service connection to your MySQL client Database. Firstly, you will need to ensure a Self-Hosted Integration Runtime (IR) is Installed on a machine that can access both the On-Premises MySQL database and Azure Data Factory. Since you're using PowerShell, here is a sample code:
$SSHHostName = "your_ssh_host_name"
$SSHUserName = "your_ssh_user_name"
$SSHPass = ConvertTo-SecureString "your_ssh_password" -AsPlainText -Force
$MySQLHostName = "your_mysql_host_name"
$MySQLPort = "your_mysql_server_port"
$secpasswd = ConvertTo-SecureString "your_mysql_user_password" -AsPlainText -Force
$mycreds = New-Object System.Management.Automation.PSCredential ("your_mysql_username", $secpasswd)
# Create SSH Tunnel
ssh -L 3306:$MySQLHostName:$MySQLPort -l $SSHUserName -pw $SSHPass $SSHHostName
Also, ensure you modify all the answers in code to suite your configuration and make sure the script is running continuously as long as you need the connection. I hope this is helpful! Do not hesitate to let me know if you have any other questions. Please remember to "Accept Answer" if answer helped, so that others in the community facing similar issues can easily find the solution. Best Regards, Sina Salam