I am trying to amend my tax return to file my business, how do i file a loss in the amendment?

What type of business? What type of loss? If you have a sole-proprietorship,you will have a loss if expenses are more than your income.

Fill out Schedule C.   Enter your gross income and expenses.  Turbo Tax will calculate the gain or loss.  

Where to enter schedule C

https://ttlc.intuit.com/community/entering-importing/help/where-do-i-enter-schedule-c/00/26092