fortnite.com/android :

When you first launch Fortnite on your console, you’re given the option to start playing immediately or provide information to create a full Epic Games account. If you opted to start playing immediately without creating an account, then a “nameless” Epic Games account was created so you could play, but that account lacks some information: it doesn’t have your email associated with it or an Epic Games display name.

Note that the Epic Games account that was created and your PlayStation, Microsoft or Nintendo account are not the same account.

Upgrading to a full Epic Games account means that all your progress and saved data (e.g. the content of your locker and gameplay progression) can be brought with you if you play on a new platform and/or on multiple platforms. For example, if you have been playing on one Console, but would now like to play on PC, you will need to upgrade your Console account in order to bring your Console progression to PC.

How to upgrade a console or platform account to a full Epic Games Account

NOTE: You may need to enable pop-up windows on your browser.

1. Go to www.epicgames.com, look in the top right corner, and make sure you’re signed out.
2. Click on SIGN IN in the top right section of the screen.
   
3. Click the icon for the console or platform that you currently play on and want to connect to an Epic Games Account.
   • You will be taken to the website of that console or platform to sign in to your account there (i.e. if you select Playstation you will be taken to the PlayStation account to sign in using your Playstation account credentials).
     IMPORTANT: If you are playing on a Nintendo Child account, you will need to log into that account by using your Nintendo Login ID, which was set by the parent during the account creation. If you use the email and password that is associated with the Nintendo account, you will access the parental account instead.
     
4. When you sign in successfully, you will be returned to the Epic Games website and you will see a page similar to what is shown below:
   
   IMPORTANT: If you do NOT see the page shown above, then you do not have any Fortnite progression on this account. Please check that you are logging in with the platform or console username and password of the account that you use to play Fortnite on.
5. Complete all required fields.
   IMPORTANT: The email you use must not already be registered to another Epic Games Account and must be a valid email that only you have access to. It doesn’t necessarily have to be the same email address that you have associated with your console account.
   
6. To be able to create an account, you must read the terms of service and then check the box: I have read and agree to the terms of service.
   If you choose not to accept the terms of service, you will be unable to create an account.
7. Click SAVE CHANGES.