See the explanation below.
Explanation
1. Click Create a resource in the upper left-hand corner of the Azure portal.
2. On the New page, select Databases in the Azure Marketplace section, and then click SQL Database in the Featured section.

3. Fill out the SQL Database form with the following information, as shown below:
Database name: Db3
Select source: Sample (AdventureWorksLT)
Server: SQL10277521
4. Click Select and finish the Wizard using default options.
References:
https://docs.microsoft.com/en-us/azure/sql-database/sql-database-design-first-database