NEW XBOX ONE AVATARS IN APRIL

If you are on the Xbox One, all you can do is create a new avatar, by launching the app, select settings, and create a new avatar.

If you are on the Xbox 360, then the best way is to launch the Xbox Original Avatar app on Windows 10, and select settings and create a new avatar.

Xbox 360 accessories and avatar items don't work on the new Xbox One avatars

You're avatar from the Xbox 360 will carry over, however, you'll have to make a new avatar using the upgraded and more diversified Xbox One avatars app. The reason for having to make a new one is because its a new system with new models and new and detailed
ways to make your avatar more like... you. You can use the old one from the 360, however, the new ones are cool... and if you haven't gotten to editing the new ones in the new app you should.

Here's a little interesting article that was about them when they first came out.

https://www.windowscentral.com/new-xbox-avatars-2017

There are two differents apps - one for the old avatars, one for the new avatars.

You will have to install and use the old app, "Xbox Original Avatars".

There's no need to create a new account; you simply have to create a new avatar in place of your current one.

In the "Xbox Avatars" app on the Xbox One (or Windows 10), you'll have to go to the settings tab (bottom), and select "Create new avatar".

NOTE: This will completely reset your avatar. Purchases won't be lost, but certain gender-specific items won't be equippable if you choose the other gender.