Payment for the Plus edition is by credit card. The card must be a US credit card with a US billing address.
See this TurboTax support FAQ for upgrading to Plus - https://ttlc.intuit.com/questions/2586262-how-do-i-purchase-turbotax-plus-so-i-can-get-my-tax-file
To access your current or prior year online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on the Year and Click on Download/print return (PDF)
You can also get free transcripts of your federal return from the IRS - http://www.irs.gov/Individuals/Get-Transcript
