How to add Additional Storage to your Azure Deployment
Virtual machines (VMs) deployed through Azure Gallery prior to mid February, 2015 do not support Disk Expansion. If you deployed prior to this time period and want to expand the disk, you must re-deploy the VM using the latest VM image available in Azure Gallery.
Log in to the Microsoft Azure Portal.
Click on Search, and then enter Virtual Machines and select.
Click on the Instance where you want to increase storage.
On the left side of the pane, click Settings and select Discs in the dropdown menu.
Click Attach New:
Enter the disk size as per your requirement.
Set Host Caching to None:
Click APPLY.
Once the task is complete, go to Settings of the selected Instance, and then click Restart.