How to add logging & use private key option in PowerShell script

param (
    $localPath = "C:\temp\upload\*",
    $remotePath = "/test/",
    $backupPath = "C:\temp\backup\"
)
 
try
{
    # Load WinSCP .NET assembly
    Add-Type -Path "C:\Program Files (x86)\WinSCP\WinSCPnet.dll"
 
    # Setup session options
    $sessionOptions = New-Object WinSCP.SessionOptions -Property @{
        Protocol = [WinSCP.Protocol]::Sftp
        HostName = "IP_Address"
        UserName = "username"
        Password = "password"
        SshHostKeyFingerprint = "ssh-rsa 2048 dxV8kkFWYK4ofTfQdquK1f+sMrvA90BOQ3f7tEm+3k9o="
    }
 
    $session = New-Object WinSCP.Session
 
    try
    {
        # Connect
        $session.Open($sessionOptions)
 
        # Upload files, collect results
        $transferResult = $session.PutFiles($localPath, $remotePath)
 
        # Iterate over every transfer
        foreach ($transfer in $transferResult.Transfers)
        {
            # Success or error?
            if ($transfer.Error -eq $Null)
            {
                Write-Host "Upload of $($transfer.FileName) succeeded, moving to backup"
                # Upload succeeded, move source file to backup
                Move-Item $transfer.FileName $backupPath
            }
            else
            {
                Write-Host "Upload of $($transfer.FileName) failed: $($transfer.Error.Message)"
            }
        }
    }
    finally
    {
        # Disconnect, clean up
        $session.Dispose()
    }
 
    exit 0
}
catch
{
    Write-Host "Error: $($_.Exception.Message)"
    exit 1
}

$filedate = Get-Date -f yyyy-MM-dd
Start-Transcript -Path "C:\Log\Log-$Filedate.txt
Cls