Share photos using other apps and websites in Photos on Mac
You can easily share your photos to a third-party website by adding an extension for the site to your Share menu.
When you open the Share menu, you see a list of extensions that Photos already uses. To share using other apps, you can download the apps (and their sharing extensions) from the Mac App Store, then enable the extensions in the Share menu.
In the Photos app
on your Mac, click the Share button 
in the toolbar.The Share menu opens, showing the extensions that Photos already uses.
Choose More from the Share menu.
The Extensions pane of System Preferences opens.
Click Share Menu on the left, then select the checkbox next to each extension you want to add to the Share pop-up menu.
After adding the extension to the Share menu, you can select photos and share them with the third-party app or website.