Esri virtual machine images containing ArcGIS for Server, ArcGIS GeoEvent Extension for Server, Portal for ArcGIS, ArcGIS Data Store, and ArcGIS Web Adaptor (IIS) are available from the Microsoft Azure Marketplace. Use these images along with ArcGIS Server Cloud Builder for Microsoft Azure and your ArcGIS for Server and Portal for ArcGIS licenses to deploy GIS servers or web GIS sites in the Azure cloud.
Go to Microsoft Azure Marketplace and search for arcgis or esri to find the images. Download them to your Microsoft Azure subscription.
Next, install ArcGIS Server Cloud Builder for Microsoft Azure and deploy a site.