Can I go back to the W-2 section after I've moved past it? I'm filing jointly and I only entered mine when I think I was meant to enter both mine and my spouse's.

Yes, you can return to the Wages & Income Section and add another W-2. Follow the steps below.

1.  Launch TurboTax
2. Select Federal
3. Select Wages and Income
4.  Select Start  by Job (W-2)
5.  Select Add another W-2.

Refer to the TurboTax Help articles Where do I add or enter a second W-2?