As of October 2017 you cannot create a New Relic account through Microsoft's Azure Marketplace Portal. Instead, if you have an Azure ID but do not already have a New Relic account, contact New Relic Sales.
For more information, see the Azure transition information in New Relic's Online Technical Community.
Continue with the procedures to install the New Relic .NET agent with your Azure app as applicable for:
The .NET agent's support for Microsoft Azure is not the same as Infrastructure monitoring's integrations with Azure. Azure integrations have separate integration installation procedures.