You don’t need to join lemmy.world. Just a heads up.
How does sync work on pc?
You can try this guide from Microsoft https://support.microsoft.com/en-us/topic/use-apps-from-your-android-device-on-your-pc-07d3d029-236e-e71f-3561-d40d7491d435
because it’s a web app
Sync is a mobile app, but you can sign in to lemmy by going to your instance’s website (for you it would be lemmy.world). Remember, sync is only a way to view lemmy, it doesn’t power lemmy