Uploading photos from Photos Library to external websites

Even though I have designated the Photos Library as the System Library, Mojave won't let me upload photos to external websites. The icon for Photos Library is disabled inside the Pictures folder, so I can't open the library folder.

I just migrated from an old laptop running High Sierra to a new Mac mini running Mojave, so several things required adjustment before they would run on the new system. This particular snag is proving impossible for me to figure out.

Any help will be appreciated. Thanks.