"password" | ConvertTo-SecureString -AsPlainText -Force |
    ConvertFrom-SecureString

$password = "(the long string generated from above command)"
$username = "Test@testdomain.com"

$cred = New-Object -TypeName System.Management.Automation.PSCredential -ArgumentList $username,($password | ConvertTo-SecureString)

ConvertFrom-SecureString

$Password = "password" | ConvertTo-SecureString -AsPlainText -Force
$username = "Test@testdomain.com"
$cred = New-Object System.Management.Automation.PsCredential($username, $Password)