icloud acct set up on mac but iphone doesn't recognize it as my email and keeps asking me to set up new iCloud email.

hi guys,

hope someone can help me out. i created a new icloud.com email address on my mac and of course i want to add this to my iphone as well. I followed the prompts on my iphone to the point where it says to turn ON my mail. when i do so, it asks me to create a new icloud.com email account. i used the one i created on my mac and it keeps saying that the email address is taken. how do i tell my iphone that that is the email address i created for this icloud acct?

thanks,

mary