I've already filed my tax return. I made a mistake and filed my business as a sole proprietorship when I should have filed it as 2 member LLC. How can I amend this?

I originally purchased Turbotax Self-Employed and just purchased Turbotax Business.  I couldn't find my tax return to amend it with the newly downloaded Turbotax Business.  How do I amend my Schedule C to the necessary Form 1045 (to get the K-1 for myself and my business partner)?