How do I play cross platform minecraft PC and Xbox One?

The PC version has to be the Windows 10 version with the latest updates (not the java version).

I believe that requires you to make an XBL login to play on the PC. From there you can connect to other people's games using the XBL login the same way you would from XBO-to-XBO.

For cross-platform multiplayer, you'll need to be running the Windows 10 version (that you pick up from the Windows Store) & NOT the Java Edition for this. If you have purchased the Java Edition at any time, you likely have a code for the Windows 10 version sitting in your Mojang account. Log into for more details.

Please be aware that the Windows 10 version runs on the XBox Live network with the Microsoft account you have attached to your user account, so it'll appear as if you're on a console with others (except you don't need XBox Live Gold subscriptions).

The Windows 10 version is running on the Bedrock Engine, so you will be able to play with those on the Switch & the Mobile versions in addition to the XBox One… But NOT the Wii U, XBox 360, New 3DS, PS3 or PS4 (at time of writing, this may change in the future if Sony allows it).