Install the openclipart-openoffice.org package using the Synaptic Package Manager. The package is very large, so it could take a long time to download and install it.

Open an OpenOffice.org application and press Tools → Gallery. A list of available clipart should appear.

Browse the clipart until you find an item that you would like to use. To insert the item, either drag it into the document or right-click the item and press Insert → Copy.