How do I create new iCloud email

if you have not already created an iCloud account, log into System Preferences (or Settings) iCloud with your Apple ID and follow any instructions. If you have already created an account you can just log in,

Enable Mail in the list. You will be asked to create an @icloud.com address.

If you already have an iCloud account and email you can add up to three 'email aliases' - these are additional addresses (not accounts) which deliver into the same inbox as the main account. (In fact it's a good idea to give out alias addresses, rather than the main address, because if they attract spam you can easily change them.)

You should be aware before you start that once you've created an alias you cannot turn that address into a full iCloud account or move it to another account.

More information on aliases here: https://help.apple.com/icloud/#mm6b1a490a

For an iPhone first create a new Apple ID see this article https://support.apple.com/en-in/HT204316

And then follow the steps in this article to create an iCloud account https://support.apple.com/en-in/HT208681