You don't work directly on "Form 1040" using TurboTax. Form 1040 represents the summary of all the details you've entered in other Forms, Schedules and Worksheets using the various TurboTax interviews:
https://www.irs.gov/pub/irs-pdf/f1040.pdf
Since you're using TurboTax Self Employed I assume you are referring to a 1099-MISC when you say you don't have a 1099. (There's almost two dozen different "flavors" of 1099's issued by the IRS so simply saying "1099" doesn't convey much information.) Start the "Business" interview. After you fill out some general information about your business you land on a page titled "Your [Business Name] Business" with a list of interviews to complete. The first interview is "Forms 1099-MISC & 1099-K, gross receipts, sales." If you have received no 1099-MISC's or 1099-K's you can simply skip that portion of the interview. You simply enter you revenue from your own books and records under "General income" , i.e., income not reported to you on a 1099-MISC.
Tom Young
