Run these Commands on Powershell ISE.
Connect-AzureRmAccount
New-AzureRmResourceGroup -Location CentralUS -Name armdemo
Create a storage account name it as armdemonested then add blob container and upload the two .json file in the container.
Set-AzureRmCurrentStorageAccount -ResourceGroupName armdemo -Name armdemonested
$url = (Get-AzureStorageBlob -Container test -Blob Demo1ParentTemplate.json).ICloudBlob.uri.AbsoluteUri
New-AzureRmResourceGroup -Location CentralUS -Name armdemo3
New-AzureRmResourceGroupDeployment -ResourceGroupName armdemo3 -TemplateFile $url
New-AzureRmResourceGroupDeployment -Mode Complete -Name ExampleDeployment -ResourceGroupName "enter your resouce group name " -TemplateFile c:\MyTemplates\Demo2CompletevsIncremental.json.json