You’ll have to convert your anonymized Apple account into an account that will be more closely tied to your identity and email address. Fortunately, this isn’t too difficult.
Move from Apple ID to Epic Games
This isn’t too hard, actually. I’ve done the same thing for websites to remove Facebook access for slightly improved privacy. Though, with Facebook, one small mistake is all it takes for them to build a complete profile on you.The idea is to log on and change your information so it links to your actual email address and personal information.
First, go to the Epic Games Login page.
After you sign in, you should see your personal details page. You’ll notice your email address will look like random characters. This is because it’s an automatically-generated email address, so Epic can’t track you across different platforms and services. Unfortunately, you’re going to have to give them your real email address now.
You may also want to update any other information here as well.
Next click Password & Security
Change your password by requesting a reset. Apple stored this before, now you’ll have to. I recommend a password storage solution like 1Password or Lastpass.
With that, you’ll have converted your account over. If you don’t do this now, you could lose access to your account, and Epic may not be able to recover it for you.
If you have any problems, you can view Epic’s help page on the topic here, which you can also use to contact support.
Source: Killian Bell, Cult of Mac