Explanation

Step 1: Create an Azure Policy Initiative
The first step in enforcing compliance with Azure Policy is to assign a policy definition. A policy definition defines under what condition a policy is enforced and what effect to take.
With an initiative definition, you can group several policy definitions to achieve one overarching goal. An initiative evaluates resources within scope of the assignment for compliance to the included policies.
Step 2: Create an Azure Policy Initiative assignment
Assign the initiative definition you created in the previous step.
Step 3: Run Azure Policy remediation tasks
To apply the Policy Initiative to the existing SQL databases.
Reference:
https://docs.microsoft.com/en-us/azure/governance/policy/tutorials/create-and-manage