Adding a second iCloud email address to my iCloud account

1. Go to iCloud.com and sign in with your Apple ID.
2. Click Mail.
3. Click the gear icon on the bottom left of the window.
4. Click Preferences.
5. Click Accounts.
6. Click Add an alias…
7. Enter an alias for your iCloud email address. ... 
8. Click OK.

If you want to add a second iCloud account on your device, go to Settings>Mail,Contacts,Calendars>AddAccount>iCloud and enter a different Apple ID. Secondary accounts can only sync mail, contacts, calendars, reminders and notes (not bookmarks, iCloud backup, photo stream, Find My iPhone, etc

Hope that answers your question.

Welcome :)