Yes, you can do this. I just did this and here the steps I took
Signed in to account with the IRS FREE EDITION
Exit out the browser (DO NOT SIGN OUT)
Open browser again and go to https://turbotax.intuit.com/personal-taxes/online/
PICK THE ONE YOU WANT TO DO
WHEN SCREEN LOADS IT ASK YOU DO YOU WANT TO SWITCH FROM IRS FREE TO THE EDITION YOU CHOOSE
