On the main screen, right click to bring up the bottom menu.
Select the playback option.
Here you can search for recordings by modifying the date/time as well as selecting the cameras you want to see footage from with the tickbox next to the channel with that camera on.
Once you have video files from the times and places you want to see you can either double click them to go in and view the file or select one or more using the tickbox in the top right.
Once selected you can use the play or backup options along the bottom.
Backup will allow you to export them to a removable USB hard drive.