That first link now takes you to Amend 2019. 2018 is missing. Use this article. It is for 2017 but will be the same for 2018. Just change all the dates to 2018 like .tax2018
https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/00/27371
