Are you saying you go to icloud.com and login and are not seeing your mail there? Or are you referring to your icloud account when you open your mail application on your computer?
If it's on your computer, make sure you have a check mark beside 'mail' in your icloud system preferences. If you do already have a check there, click on account details, and make sure the email address that shows up there is your apple id, to which your icloud mail account is associated.
Otherwise... more details please.