...with a space at the end (and do NOT press enter yet).
Then, drag the file you want to change from the Finder and drop it on top of the Terminal window. The file path and filename should automatically fill in (and you should ensure that there's a space between "+x" and the file path).
I found the solution...
https://macosx.com/threads/change-a-plain-text-file-to-unix-executable-f...
Open Terminal.
type...chmod +x
...with a space at the end (and do NOT press enter yet).
Then, drag the file you want to change from the Finder and drop it on top of the Terminal window. The file path and filename should automatically fill in (and you should ensure that there's a space between "+x" and the file path).
Press enter.
This changes the file to an executable.