In addition to my home office I also now use my garage solely for inventory and product samples, how do I show that?

You can deduct your garage in your home office deduction if you meet certain qualifications.

This, from Publication 587, Business Use of Your Home:

Storage of inventory or product samples. If you use part of your home for storage of inventory or product samples, you can deduct expenses for the business use of your home without meeting the exclusive use test. However, you must meet all the following tests.

You sell products at wholesale or retail as your trade or business.

You keep the inventory or product samples in your home for use in your trade or business.

Your home is the only fixed location of your trade or business.

You use the storage space on a regular basis.

The space you use is a separately identifiable space suitable for storage.

Once you have determined that you can use the space as a home office, simply add it to your home office.  For more, see this:

Steps for Home Office

To enter into Turbo Tax Self Employed:

1. Click Federal on the left-hand side tab.
2. Click Income & Wages along the top.
3. Scroll down to Self Employment, and click Show More.
4. Click Start or Revisit by Income and Expenses.
5. Click Review by your Business name.
6. Click through till you get to Your Business Income and Expenses.
7. Scroll down till you get to Home office deduction, and click Start or Review.
8. Answer the questions till you get to the screen below.