Do i need some proof of earnings from foreign company while working overseas?

[slovensaric]

how do i show foreign earned income on 1040?

[DoninGA]

You always need some type of proof of income for the amounts entered on a tax return in case the IRS ever questions your income entries.

To enter Foreign Earned Income -

Click on Federal Taxes (Personal using Home and Business)
Click on Wages and Income (Personal Income using Home and Business)
Click on I'll choose what I work on (if shown)
Scroll down to Less Common Income
On Foreign Earned Income and Exclusion, click on the start or update button

[Hal_Al]

You do not submit/file any proof  of your earnings with your tax return.  That comes later, if the IRS makes inquiries about your tax return filing.