Hey @Raviteja Kotha
This Microsoft documentation should guide you in creating a custom DSC resource with PowerShell https://learn.microsoft.com/en-us/powershell/dsc/resources/authoringResourceClass?view=dsc-1.1
But before you dive into that I recommend watching this video walkthrough by Gael Colas Writing DSC Resources for Azure Policy Guest Configuration - For Linux!
Hope that helps