You can add media to the Media Library using the Upload option in the Oak menu.
Before uploading, make sure you publish the media to an area that the intended users have permission to view. You can also use folders to control visibility for different groups. For example, a Marketing folder could be restricted so only the Marketing team can access its media.
When creating content, the media picker shows media from the Media Library, your 14 most recently uploaded personal images, and Oak stock media.
Images uploaded directly through the media picker are personal to the user who uploaded them and are not available to others. To make media available for wider use, upload it through the Upload option and publish it to an appropriate area.