An Azure relational database service.
There is no SQL Server Management Studio 2018. The most recent version is 22.7.2, which you can download here: https://docs.microsoft.com/en-us/sql/ssms/download-sql-server-management-studio-ssms.
It is not clear what you have. SSMS alone will take you nowhere. You either need to have SQL Server installed locally on your own computer or in your network. Or you need to have a database in Azure. For the latter you need to have an Azure account, and you create the database through the portal. There is a free offer that you take advantage off.