Perform the following in the Azure Console:

1. Go to SQL databases
2. For each DB instance
3. Click on Transparent data encryption
4. Set Data encryption to On

Perform the following in Azure Command Line Interface 2.0:

Use the below command to enable Transparent data encryption for SQL DB instance.

az sql db tde set –resource-group <resourceGroup> –server <dbServerName> –database <dbName> –status Enabled

References:

1. https://docs.microsoft.com/en-us/sql/relational-databases/security/encryption/transparent-data-encryption-with-azure-sql-database