Hi Lonewolf2Koc,
Thanks for your question. The "How do I export MXF files?" section of this support article has the steps you need to export MXF files from Final Cut Pro X. I've highlighted the key information here for you. Click on the article for complete details.
How to use Pro Video Formats and MXF with Final Cut Pro X, Motion, and Compressor - Apple Support
https://support.apple.com/en-us/HT204322
To share an MXF file from Final Cut Pro, follow these steps.
- In Final Cut Pro, choose File > Share > Add Destination.
- Select Compressor Settings, open the Custom folder, then open the MXF folder.
- You'll see multiple MXF settings. Pick the one that matches the frame rate you need to deliver. Inside that folder are more choices for codec and frame size. Again, pick the setting that is appropriate for your delivery needs.
- Your choice will be added to your list of default settings in the Share menu. Continue with standard Share steps to save the shared MXF file.

If you’re sharing from Compressor 4.1 or later, the MXF presets will appear in the Settings pane under the Custom header. Click the disclosure triangle to see the various frame sizes and codec options available.
Have a great day!
- Judy