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The Xbox Live Creators Program is a good starting point for Xbox Live if you are looking to familiarise yourself with Xbox Live development. No approval process from Microsoft is required to join this program, and there are minimal certification and publishing requirements. A Microsoft Developer account is required.

You need this to get it done:

Microsoft Account
You'll need to sign in with a Microsoft account that you want to associate with your developer account. If you don't already have a Microsoft account, you can get one when you start the signup process.
Registration Fee
Creating a developer account requires a one-time registration fee. Individual accounts cost approximately $19 USD, and company accounts cost approximately $99 USD (the exact amounts may vary depending on your country or region). You can make this payment with Visa/Mastercard, PayPal (in supported locations), or a promo code. Note that prepaid credit cards are not accepted.
Product Name
The name of your product, which will be requested when you click "create a new app" inside the Partner Center dashboard. You can change the name later. Once you reserve a name, your app will be provisioned for services like push notifications and you can start defining add-ons. Make sure you have the rights to use any name you reserve. You must submit this app to the Microsoft Store within three months, or you'll lose your name reservation.
In the "Pick a category" drop-down list, select the "Games" category. Do not select a category other than Games, or else the Xbox Live options won't be available.
Select one or more check boxes which are most appropriate for your game (e.g. Action + adventure, Platformer, etc.)
Xbox Live Game Name
When you are enabling Xbox Live for Creators for your game, enter the name of your game in the Xbox Live game name text box. This can be the same as the name of the game you specified at the beginning, but it doesn't need to be the same.
Select the platforms that you would like to enable the Xbox Live Services for. Both Xbox One and Desktop are selected by default.
Xbox Account for Testing
If you don't have an Xbox account that you want to use for testing, create one.
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How-To Articles
A list of useful links for you:

Microsoft Docs - Choosing an Xbox Live Developer Program
An overview of the Xbox Live Creators Program, and how it is different from the ID@Xbox Program.
Microsoft Docs - Joining the Creators Program
Step-by-step guide for joining the Creators Program.
Microsoft Docs - Setting up a Game at Partner Center (for Creators)
Step-by-step guide for creating a new game in the Partner Center.
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