Trying to amend 2018. Have made amended file but can't get to where you search for amend and start. How do I begin?

Received a K1 after 2018 taxes had been filed and received.  Need to amend but unable to get started.  I opened the return and saved it under "amended" but next step was to search for amend and then "jump" and how do you do that.  I see no search available