Welcome to Apple Support Communities. I understand that you'd like to know how to use iTunes on your MacBook to remove podcasts synced to your iPhone X. I can see why you'd reach out for assistance with this; I'm happy to help. To add or remove podcasts to the Podcasts app on your iPhone use the steps below:
Sync your iPhone, iPad, or iPod touch with iTunes on your computer using USB
- Open iTunes. Make sure that you have the latest version.
- Connect your device to your computer using the included USB cable. Your connected device appears as an icon in the upper-left corner of the iTunes window. Learn what to do if you don't see the icon.
- Click on the device icon . Look under Settings on the left side of the iTunes window for a list of the content types that you can sync from your iTunes library to your device.
If you don't have certain content in your iTunes library, you might not see some tabs. For example, if you don't have any podcasts in your library, you won't see a Podcast tab.
iTunes can't sync certain content, including mail accounts, notes, or bookmarks. Use iCloud to manage your mail, notes, and bookmarks across your devices. Some iOS apps might use iTunes's File Sharing feature to transfer content instead of syncing.
- Click the content type that you want to sync.
- In the main iTunes window, click the box next to Sync to turn on syncing for that content type. If there's a check in the box, syncing for that content type is already on.
If you see a message that your iOS device is synced with another iTunes library after clicking the box, your iOS device was previously connected to another computer. If you click "Erase and Sync" in that message, all content of the selected type on your iOS device is replaced with content from your computer. Content that you didn't turn on syncing for isn't deleted from your iOS device. You can only sync your iOS device with one iTunes library at a time.
- After you turn on syncing for a content type, you'll see additional options to customize your sync settings. Use these options to make sure that you're syncing the content that you want synced.
- Repeat steps 4–6 for each content type that you want to sync.
- Click the Apply button in the lower-right corner of the screen to save your sync settings. If syncing doesn't start automatically, click the Sync button.
After you turn on syncing, your content syncs each time that you connect your iOS device to your computer and have iTunes open.
If you see a message that some of your content couldn't sync, your computer might not be authorized for that type of content. Make sure that your computer is authorized for the content that you're trying to sync.
Since you're wanting to remove certain data, you'll want to follow the steps above to enable syncing for Podcasts and uncheck the content you'd like to have removed when you sync.