The 1040 is your tax return that you are filling out . You enter your W2 and any 1099 forms you get. When you are done entering all your income and deductions and any dependents you go though the File tab and efile it to the IRS by hitting the big orange Transmit Return Now button.
Here is a blank 1040 form to see what you are filling out
https://www.irs.gov/pub/irs-pdf/f1040.pdf
