Screenshot permissions on external drive

So, I have my screenshots set up (via the Terminal command) to save to my NAS. However, because of the new permissions request in Catalina, they will not save there, and I don't know how to enable the permissions. (It just gives an error "Your screen shot can’t be saved. Cannot write file to intended destination.")


(For now, I reset the screenshot folder to the Desktop, but I'd like to change it back to my NAS.)