I'm trying to get my previous years tax return and I don't see the option to upgrade to PLUS. they are only tryng to give me deluxe. help ??? I need this for school.

In the Upgrade section of your 2018 return is PLUS grayed out?  If so, that means you are already in PLUS and just need to pay the 19.99 by credit/debit card.  We can tell you the steps once you clarify your situation.  Whatever you do, do NOT upgrade any further past PLUS, or you'll have problems.

Is access to the 2017 return locked, and it asks you to pay?   

Have you already filed your 2018 return with Online TurboTax, or is it still in preparation?

Are the 2017 and 2018 returns in the same account?

We can tell you how to pay once you answer all the above.

There's also a free option if a return transcript will suit your purpose.   You may be able to immediately download one at the IRS website if you qualify to open an IRS account there.  Otherwise, to order a transcript to come by postal mail takes 5-10 calendar days.
http://www.irs.gov/Individuals/Get-Transcript