You enter your self-employment income as business income. When you enter it there will be a place to enter your EIN, which will appear on Schedule C. But it's still included in your one tax return, along with all of your other income.
"No you do not need to file a separate tax return."
It's not just that you do not need to file a separate tax return. You cannot file a separate tax return unless your business is a partnership, S corp, C corp, or multi-member LLC.
