How do I add an already existing iCloud to my mailbox on my IPhone 6

On my phone I created I second email and then had two sperate email accounts

I then undownloaded the default mail app and re downleaded it

but when I did that the first email seemed to have just disappear from the app (i can still use messages and other apps with it though). And the second email still gives me emails and everything just as it did before

And when I try to add the original email back it doesn’t come up as an option anywhere (not even in settings)