Accrual Method for Inventory

I have a question on the Accrual Method and what it means for inventory tracking and reporting. I am self employed and have inventory I sell and also teach fitness classes as part of my business. TT says you are required to use the Accrual Method for inventory, so I chose "combination", that I used accrual for inventory and cash for other. So...for my expenses and income/payments I received from people, I reported them as income and expenses when the expenses and sales occurred (I think that means I did this on a cash basis). For my inventory, I entered the beginning (zero since new business) and the end at 2017, and then the cost. I am not sure if this is right for the accrual method or what that means in terms of my inventory. TT did NOT ask me to separate income from inventory vs. classes, so I just put total sales for income based on date sold.  Thanks!