When you are entering information about your self-employment business, the screens may ask you things such as whether you had employees, whether you had someone do work FOR you where you gave them a 1099 form (so this wouldn't be related to your income or you receiving a 1099), or if you have an Employer ID number, etc. These screens can all be answered in the negative that you didn't have employees, a 1099 contractor, or an employer ID number. After these screens, a summary will be shown where TurboTax asks you to review your self-employment business. If you select "It looks good" you should then proceed to the screen to enter your income. There should be an option to "select additional income and other income: includes 1099K, cash, checks and other income." Selecting this option should allow you to enter the type of income received and the amount.
To find this section again, type "Schedule C" in the search field on the upper right of the screen and select "Jump to Schedule C" and you will be brought to the entry screens for your self-employment income as described above.
