Microsoft is launching the preview of Skype for Outlook.com, starting with the UK and will make its way to the US and Germany in the coming weeks. Skype for Outlook.com requires for you to download a plugin, which is available for internet Explorer, Chrome and Firefox. Users can connect their existing Skype accounts to outlook.com or use their Microsoft account to use the service. If you use your Skype account you will be able to add your Skype friends to email contacts of outlook.com.
There are much detailed step-by-step instructions here at the Outlook blog.