Crucial SSD firmware update

About six month ago I mount into my MacBook a new Crucial SSD (MX 200) that works well everytime but now there is available a firmware update on Crucial website: I follow this steps but when I try to open mx200_revMU04_bootable_media_update.iso (as in above online guide step 3) I receive the following error: The document "mx200_revMU04_bootable_media_update.iso" could not be opened. Disk Utility cannot open files in the "ISO Disk Image" format. Crucial support say me to "Open Image File" and then select the firmware ISO or burn firmware in a different system: when I selected "Open Image File" in Disk Utility I am not able to see the "Burn" button so I follow this Apple official article to burn ISO file into my CD-RW but when I shut down my Mac and then power on it again (with press and hold Option key) I can't see CD with firmware updater, only Macintosh SSD and Recovery partition.

Anyone can help me?