Automatic failover allows Cosmos DB to failover to the failover region with highest priority. Account must have two or more regions to enable automatic failover.
a) Log on to the Azure Portal.
b) Select the provisioned "Azure Cosmos DB" and click on "Replicate data locally".
c) Click on "Enable" multi region writes and "Save".
d) Add multiple regions as availability zones and "Save".
e) Now your Cosmos DB has 3 failover availability regions providing high write and read availability.