It shows at the top or bottom of the product description, social share and like buttons from LINKEDIN, TWITTER, GOOGLE PLUS, FACEBOOK (iframe or XFBML) + Short url service. It installs via the regular Joomla installer. Enable it and also make sure content plugins are enabled in VM configuration.
http://www.nordmograph.com/en/downloads/details/110/151/virtuemart-plugins/vm2-share-plugin-for-virtuemart.html