In order to generate your letters, you have to fill out this form. This form can be used to dispute anything on your credit report. Just take your credit report, highlight the negative items and fill out the form. Once, you are finished, the app will generate the letters that you can send to the credit bureaus (Transunion, Equifax, Experian).
Send every single generated letter separately to the bureaus. It will increase your chances of deleting those negative items.
Also, MAKE SURE YOU STAPLE a copy of your social security card, driver's license and a utility bill to each letter generated by the app.