If you’d like to make a Gallery from your collection public or private, you can do this by selecting the Gallery and then clicking the three dots button, then clicking the Edit button.
Once you have done this, you'll be redirected to the Edit Gallery page.
If you want the gallery to be public select "Visible to everyone"
If you want the gallery to be private select "Only visible to me"
Once you have make the necessary changes, make sure you hit Save changes.