how can I create an iCloud email?

If you log into your Apple ID, you should already have an @iCloud.com email address. You also might have an @me.com and/or an @mac.com address. See below if you want to create an alias email address.

iCloud - Create or change email aliases.   

You basically know how since you created the one you needed to sign in here. But if you want another new one, see:

How to create a new Apple ID https://support.apple.com/en-us/HT204316 and

How to switch Apple IDs on your iPhone or iPad

https://www.imore.com/how-change-apple-id-your-iphone-or-ipad

See the data implications below.

Some of these things may apply even though not changing an Apple ID: What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071

 Keep in mind that some things available under a first Apple ID will not be available under a new Apple ID. For example, you won’t be able to transfer anything purchased from the App and iTunes Stores to the new ID. And, there are other issues to be addressed.

And see what Eric Root says on this matter here  https://discussions.apple.com/thread/251483565and

what Winston Churchill says about it here: https://discussions.apple.com/thread/7452747

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You also can set up family sharing between the IDs to share purchases made with them. See:

Family Sharing  https://support.apple.com/en-us/HT201060

Set up Family Sharing https://support.apple.com/en-us/HT201088