I am trying to back up my files to Icloud, but i cannot find the Desktop and documents folder option under Icloud options. Is there a step i am missing?

Hello,

I have folders on my mac's desktop that I want to back up to my Icloud account. I followed the instructions of clicking on the apple-systems preference- Icloud drive- options- select Desktop and documents folders. The problem is that Desktop and document folders is not showing as an option. Is there a way for me to get that option to back my files?