To listen to audio of the entire talk, make a choice from the sound menu (at left). Otherwise, select a section from the pictures menu and you will be offered the audio that goes with it (if available). You will need a player for the desired format (and speakers, a soundcard, operating system drivers, etc.). More help is available.
Select a thumbnail from the menu on the left; The large version will appear here. If the image is too big, you may wish to resize your browser window or adjust the width of the menu.