To open snapshots in other applications, you must first export them as bitmaps. It's possible to export them one at a time using File/Export, but for large numbers of snapshots this becomes tedious. Export All allows you to export multiple snapshots at once, using the same settings for all of them.
To export multiple snapshots, first load them, and then select Snapshot/Export All. Whorld displays a folder dialog, allowing you to choose a destination for the bitmaps. After you select a folder and press "OK", the Export dialog is displayed; configure the options as desired, and press "OK" to begin the export.