You can't enter your foreign income in the W-2 section of TurboTax. TurboTax is asking you to complete Form 4852 because you entered the income in the W-2 section and checked the box that says you "need to complete a substitute form." Form 4852 is the substitute W-2 form. But a substitute W-2 is for U.S. income for which the employer should have given you a W-2, but didn't. It's not for foreign income.
You have to enter your foreign earned income in the foreign earned income topic. Follow the instructions that SweetieJean gave you. When it asks you what form your foreign income was reported on, select "A statement from my foreign employer (could be cash)."
