If you're looking to get mobile builds on your Xbox, there are a few things you'll need to do. First, you'll need to have an active Xbox Live account and be signed in. Next, you'll need to download the Windows 10 Insider Hub app from the Microsoft Store. Once the app is installed, launch it and select the 'Insider content' tab. From here, select 'Show all'. You should now see a list of available Insider content. Find the program you want to install (in this case, Mobile Builds) and select it. Finally, follow the on-screen prompts to complete the installation process.