There is more to it than deleting the DBs that you created; there are all of the server principals (users) as well.
As @CHill60 suggested, SSMS would be the best tool to get and then you can delete away on an as needed basis.
You can retrieve a list of all databases not created by
SA (System Administrator) by using
SELECT [Name] FROM sys.databases where owner_sid <> 0x01
You can delete a DB via code as well
DROP DATABASE [DatabaseName]
There is a similar query for the server-principals, and a similar
DROP command
Experienced SQL Users could right a quick cursor and utilize
Execute sp_ExecuteSql to do this, but I would highly recommend against it