You may create users from logins at SSMS.

Go to "Logins" beneath "Security" in Microsoft SQL Server Management Studio and double-click a particular login to open the "Login Properties" dialog box. Go to the "User Mapping" option at the upper left. This will show a list of your databases with checkboxes by them. Those databases with checked checkboxes have users for the Login. Checking a checkbox creates a user for the login at the database.