You're in luck: creating a new class is easy in MindTap.
Go to www.cengage.com. Click on "sign in" to get to your instructor account. Once you are there, you should see the product you've been using. If you are still using that same textbook, then click on "Create Course" underneath it. You can copy your course from the previous semester. Then, you can make changes to dates, new assignments, organization, etc. And this new course will also have a new course ID for you to give your students so they can be sure to enroll in Spring 2019.
Good luck! Let us know if you need further assistance, and best wishes for a great upcoming semester.
If this is your first class using MindTap (or any Cengage product), I would encourage you to contact your campus Cengage rep. or a digital learning specialist (assigned by the rep. usually) to create the course for you. Once you have it, you can use it to create new classes in future semesters by copying it over (if there are no major changes). Our consultant typically creates my course sections (and all of the other sections of the course which I coordinate) just to avoid any errors/issues.
Hope this helps.
It is SO easy you will be amazed! Follow @Audrey_Wick instructions and VOILA, you will have your course created in less than 5 min!
As @sinjini_mitra said, you might want to have a DSS help you through this when you get to the fine-tuning of hiding materials and adding dates. Good luck and have a wonderful semester!