To view a file (KI) placed in a Sagan, simply double-click it. Most file-types will open in a new tab (i.e. images, docs, urls) and other file-types (audio and video) can be downloaded to your computer for viewing.
To view files close-up without leaving the app, you can engage the in-app viewer by selecting the KI, then clicking the KI name at the bottom of the screen (files unsupported by the viewer will be downloaded).
From here, if the eye button is enabled, you can still open the file in a new tab.
You can also download downloadable files using the download button
Close the viewer by clicking the 'x' button at the top