RDM cmdlet - how to set credentials of WebBrowser entry

Hey i have a list of website login with password which i would like to add in bulk to RDM. I tried creating one with the following Powershell commands in RDM cmdlets:
$name = "sample"
$url = "http://www.sample.com"
$email = "myuser@email.com"
$username = "myusername"
$password = "mypassword"
$namewithaccountinfo = $name + " (" + $email + ")"
$session = New-RDMSession -Name $namewithaccountinfo -Host $url -Type WebBrowser;
Set-RDMSession $session -Refresh;
Update-RDMUI;

Set-RDMSessionUsername -ID $session.ID $username ;
$pass = ConvertTo-SecureString $password -asplaintext -force;
Set-RDMSessionPassword -ID $session.ID -Password $pass;
Set-RDMSession $session -Refresh;
Update-RDMUI;
However the credentials part remains empty... How can i set it?