I think that I found the solution, or at least a solution (it does not seem ideal).
I typed this:
sudo chmod -R 755 ./directory
and it works.
But, this leads to questions:
1. There must be one command to change permissions for all subdirectories?
2. why ./articles and not just articles? When using chmod on my webhost server, I never typed ./ to change permissions for a directory (I use Jumpline.com if that helps at all).
3. Most important question – is this the correct thing to do, or are there security risks once I go online with my website? Security is something that I know nothing about (yes, even less than I know about Linux in general!) and I keep seeing threads about it, which worries me.