Skype for Outlook.com requires a one-time download of a plugin for your browser (available for the most recent versions of Internet Explorer, Chrome and Firefox). After you download the plugin, simply connect Skype to Outlook.com using your Microsoft account.
Customers with an existing Skype account will be asked to link Skype and Outlook.com in a few simple steps. Just merge your Microsoft and Skype accounts and you’re off and running. This will also allow you to add all of your Skype contacts to Outlook.com contacts.
For more details on the new service checkout the Skype Blog.