Programmes which support Audio description have the symbol [AD]. You can check for the icon on GUIDE or by pressing the 'i' icon on the remote control for a selected programme.
To enable the Audio description, go to Settings -> Accessibility -> Audio trace and subtitles.
Select the audio description setting from your remote control and confirm by pressing OK.
You can also enable 'audio description' by playing the programme and selecting the setting icon on the panel displayed at the bottom of the screen. Use the right key on the remote to select 'Audio description'.