I forgot to add my Amazon business purchases to my business expenses and it adds up to about $1500. I already submitted my taxes? Is there anything I should do?

You will have to be patient and wait for the original return to be processed.

You're right, a $1500 business expense will be significant, but filling an amended return before the initial one is finalized can significantly complicate things,

Here are steps to amend a current tax return.

TurboTax Online

1. On the Tax Home screen, scroll down to Your tax returns & documents and select the year you want to amend.
2. Select the Amend (change) return dropdown, 
3. Then Amend using TurboTax Online. 
4. If you're told to amend your return via TurboTax Desktop, follow the steps for TurboTax Desktop instead.
5. Continue through the screens,
6. Make the changes you need to make, and carefully answer the remaining questions to finish amending your return.

TurboTax Desktop

1. Open the TurboTax Desktop software for the year you're amending. 
2. Under Need to Amend a Filed Return?, 
3. Select Amend a Filed Return.
4. Select Amend for the return you need to amend. 
5. If the return you need doesn’t appear as an option, select Find a Tax File to find and load the return.
6. On the Do you need to change anything else screen, 
7. Select Update next to the info you need to change.
8. Continue through the screens, 
9. Make the changes you need to make, and carefully answer the remaining questions to finish amending your return.
10. Don’t forget to select Save As (or Duplicate on Mac) from the File menu when you save a copy of your amended return. 
11. This will preserve the tax return you originally filed. Give the file a different name from the original, like [tax year]_TurboTax Online

How do I amend my federal tax return for a prior year?