Login to the portal https://portal.azure.com/ with the desired credentials.
Click on “More Services >” from the left navigation bar and in the search by category section, type “Elastic” and select the “SQL elastic pools” from the listed options.
Select the preferred elastic pool from the SQL elastic pools.
A new window opens with “Overview” of the SQL elastic pool and Click on “Configure Pool” from the top navigation bar.
Under Configure Pool section, select the option “Add to pool”.
A extension window of “Add databases” opens and check the database which needs to be added and click on “Select” button.
The database will get added to the “Databases selected to be added” section and the status of the database will be “Pending”.
Click on “Save” button from the top navigation bar to complete the action.
It will take time depends on the database to complete the changes. The progress can be viewed under the “Notifications” button from the portal top navigation bar.