Hi and welcome to the forum 
To help others help you better you need to provide more details about the steps you did before you hit your problem…
Start with:
- Which Operating system do you use normally,
- Which Manjaro image did you download,
(Give the URL) [HowTo] Post screenshots and links - Where did you store that Manjaro image,
(USB-Stick / CD/DVD / Harddisk) - Did you check the image using it’s checksum / hash files?
Check a Downloaded ISO Image For Errors - Manjaro - How do you start that Manjaro image.
(Do you boot your computer with it or do you use a Virtual Machine) - Do you have
Secure Bootenabled in your UEFI-BIOS.