Here is something I posted elsewhere this morning, I think it will help you.
You cannot use a different email address in a truly significant way and still have it associated with iCloud.com. Your Apple ID email, whether you realize it or not, is name@iCloud.com, name@me.com, or name@mac.com (i.e.,since you are signed into iCloud.com). Of the three, either or both that are not "officially" your Apple ID email, are aliases for it (assuming you can use one or the other for email). If, for example your "official" Apple ID email is name@mac.com, you can change it so that name@me.com or name@iCloud.com becomes "official" if you are able to get and send email using one or both of them. It makes very little difference which you use as your email address, although some choose to use an email alias for reasons not discussed here. For discussion of most of my points, See "How to change your Apple ID if it ends with @icloud.com, @me.com, or @mac.com." https://support.apple.com/en-us/HT202667
You also can set up a second Apple ID that uses a third-party email address, for example, name@yahoo.com. I would not do so because having more that one Apple ID can lead to trouble.