Skype Connectivity with Skype For Business (Lync)

Communicate with Skype Users with Microsoft Skype for Business
This document shows users how to use instant messaging, audio calls, and presence information to communicate with Skype users while using Microsoft Skype for Business (and vice-versa). As of November 2014, Microsoft announced that the “Lync” application would be named “Skype for Business” instead. The name change will be formally applied in early 2015.
Microsoft Skype for Business supports connectivity with Skype. This connectivity allows Skype for Business users add Skype contacts by using the Skype user’s Microsoft Account (MSA).Skype users can also add Skype for Business users to their contacts list. Skype for Business and Skype users will be able to communicate using instant messaging, see each other’s presence, and initiate audio calls.
Microsoft Accounts (MSA)
If you use an email address and password to access services such as Microsoft OneDrive, Windows Phone, Microsoft Xbox LIVE online game service, Microsoft Outlook client, Microsoft's Hotmail or Windows Live Messenger, you already have a Microsoft Account. If you also have a Skype account, its easy set up single sign-on to access a variety of additional applications and services, including Skype for Business-to-Skype voice calls, etc.
To set up a Microsoft account, see the Microsoft account sign-up page.
Using Skype with Skype for Business
If users sign in to Skype with a Microsoft account, they may use Skype to communicate with their non-Skype contacts who are using Skype for Business (and vice-versa). For instructions on how to link your Skype and MSA accounts, go to the Skype Support Page.
Note: Be sure to link your Skype account to an MSA. A Skype account that is not linked to an MSA will not be able to communicate with Skype for Business users.
For the full article, please follow this link. It will take you to the UWC Knowledge Database article on Skype Connectivity.