To open image file in Handy Viewer you can simply double-click on it in Explorer, or select in the popup menu: Open With -> Handy Viewer
Another way is to open a file directly in Handy Viewer. Click the following button on toolbar:
In the dialog window select desired file(s) and click "Open".
Alternatively, you can drag and drop and files from Explorer to the Handy Viewer window.
To open a file from the list of recent files, in the main menu select: File -> Open Recent -> choose desired file in sub-items.
To reopen the current image (open original , not modified file), click File -> Reopen.