How do I switch from IRS free file to paid edition?

There is no process for you to upgrade from the Free File Program to the TurboTax online editions.

You will need to start a new tax return using the online editions with a new User ID - https://turbotax.intuit.com/personal-taxes/online/

Turbo tax may have fixed this because I was not finding a way to switch to a paid version after starting the federal free file product.  I clicked your link and answered the boxes about my tax situation and it recommended Turbo Tax Premiere.  I logged in, still throufh the link and it asked if I wanted to switch from gederal free to Premiere.  I confirmed and my information was all transferred over to the Premiere product.  I am glad it did as it was a couple hours worth of work.

I found a trick. Adjust your income that will disqualify you from IRS free file and then make the switch to the version you like. You can start over then as well