Someone here may be able to help you if you have a specific question.
However, the form is not supported by TurboTax.
About Form 843, Claim for Refund and Request for Abatement | Internal Revenue Service (irs.gov)
here's the form and instructions from IRS website. post further question in this thread.
https://www.irs.gov/site-index-search?search=843&field_pup_historical_1=1&field_pup_historical=1
Form 843 is not included with your regular tax return and is not supported by Turbotax. It is filed separately by mail when you need to make certain refund claims. Someone may be able to offer help if you have specific questions.