1. Open Powershell as Administrator.
2. Import Navision Cmdlet, if you are using the Powershell ISE
import-module “C:\Program Files\Microsoft Dynamics NAV\100\Service\NavAdminTool.ps1”
3.New-NAVServerUser -ServerInstance <<NAV Server Name>> -WindowsAccount <<Domain\UserName>> -LicenseType Full -State Enabled
4.New-NAVServerUserPermissionSet -PermissionSetId SUPER -ServerInstance <<NAV Server Name>> -WindowsAccount “Domain\UserName”