After you file
It's possible that you have multiple accounts.
Check here and follow the prompt. If you do have multiple accounts, they'll all show up in the email it sends you.
Once you're in the account you filed with, you can find your return here: 
"Other ways to get a prior year return:
- Order a free tax return transcript online or by mail from the IRS that has a lot (but not all) of the information from the return. Some people may not be able to do this.
- Pay the IRS $50 for an exact copy of your return."
Cited from FAQ: How do I access my prior year (2017) return?
