Add-Type -Path "C:Program FilesCommon Filesmicrosoft sharedWeb Server Extensions16ISAPIMicrosoft.SharePoint.Client.dll"
Add-Type -Path "C:Program FilesCommon Filesmicrosoft sharedWeb Server Extensions16ISAPIMicrosoft.SharePoint.Client.Runtime.dll"
$siteUrl = "https://contoso.sharepoint.com"
$adminUsername = "admin@contoso.onmicrosoft.com"
$secureAdminPassword = Read-Host -AsSecureString "please enter password"
$credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($adminUsername, $secureAdminPassword)

$credential = Import-Clixml  "C:somepathsecurePassword.xml"

$plainPassword = "Plain text"
$secureString = ConvertTo-SecureString $plainPassword -AsPlainText -Force