To schedule a Skype meeting from Outlook, click Calendar (Ctrl+2), and click New Meeting. Configure your meeting like you always would, setting the time and inviting names, but don't click Send just yet.
Next, you click Skype Meeting at the top, found just to the right of the Scheduling Assistant.
Now you can click Send.
Note: If the user doesn't have Skype application installed they will use the web version of Skype for Business.
Want to know what the user on the other end will see for the web version, click here.