Adding a yahoo alias email address on iphone

How can I add an alias/second yahoo email address to my phone mail? I try to add but it says I already have a yahoo email address.

On my iPhone I go to settings, mail, accounts, add new, then go through the steps by choosing yahoo and entering my 2nd email address and password, but then it says that I already have a yahoo account setup on my iPhone. Then I try to set it up manually by choosing other and it still won’t work. I want to be able to choose the email address that is shown when I send emails. It used to show but then it said my pswd was wrong so I reset it and it still said it was wrong so I deleted the 2nd email address thinking I would just re-add it bu now I can’t...