string script = @"
$Username = 'admin'
$Password = '1'
$SecurePass = ConvertTo-SecureString -AsPlainText $Password -Force
$Cred = New-Object System.Management.Automation.PSCredential -ArgumentList $Username,$SecurePass
Invoke-Command {Get-Process} -ComputerName 0.0.0.0 -Credential $cred
";

ps.AddScript(script);
var results = ps.Invoke();

string script = @"
$username = 'admin'
$pass = Get-Content C:pass.txt
$pass1 = ConvertTo-SecureString -AsPlainText $pass -Force
$cred = New-Object System.Management.Automation.PSCredential -ArgumentList $username,$pass1
Invoke-Command {get-process} -ComputerName 0.0.0.0 -Credential $cred
";

ps.AddScript("C:\pass.txt").Invoke();