Step 1: Create a PowerShell configuration file
You create a simple PowerShell DSC configuration file.
Step 2: Load the file to Azure Blob storage
Package and publish the module to a publically accessible blob container URL
Step 3: Configure the Custom Script Extension on the virtual machines.
The Custom Script Extension downloads and executes scripts on Azure virtual machines.
Reference:
https://docs.microsoft.com/en-us/azure/automation/automation-dsc-getting-started
https://docs.microsoft.com/en-us/azure/virtual-machines/extensions/custom-script-windows