how do i add another email address

How do I add another email address to my Apple iCloud account?

Do you mean as an alternative email address? You can create an alias email address which is part of your Apple ID email address. Apple describes this in Add and manage email aliases for iCloud Mail on iCloud.com: "...you can create up to three @icloud.com email aliases on iCloud.com. After you set up an alias, you can send and receive mail from that alias on iCloud.com and on any device that has Mail turned on in iCloud settings."

Use email aliases in Mail on Mac

Create or change an alias

1. In the Mail app  on your Mac, choose Mail > Preferences, then click Accounts.
2. Select an account, then click Account Information.
3. Click the Email Address pop-up menu, choose Edit Email Addresses, then do one of the following:

Add an alias: Click the Add button, then enter a name and email address.

Add and manage email aliases for iCloud Mail on iCloud.com

Create an email alias

1. In Mail on iCloud.com, click  at the top of the Mailboxes list, then choose Preferences.
2. Click Accounts, then click “Add an alias”.
3. Provide the requested information:

• • Alias: the text you provide becomes the email address (alias@icloud.com). An alias must contain between 3 and 20 characters.
  • Full Name: the name you provide appears in the From field of the messages you send.
  • Label: aliases are listed alphabetically by label.

4.Click Add, then click Done.