I don't understand how to use my secondary email

I don't understand how to use my secondary email. I see that I can only send and receive mails from my primary email in Zoho Mail. I tried to log in with my secondary email but it's still my primary email. Then I tried with the Zoho Mail iPhone App, I log in with the secondary mail but it's still the primary. And finally I tried with the iPhone Mail App, tried IMAP and POP but it failed. What am I doing wrong?