The full guide is here…
For those of that already have PIC enabled (most of you i would assume)…. i found the guide to be a little bit off, in that my existing provider was called “MSN” – not “Messenger”
So, my suggestion is to open up your Lync powershell and…….
note the name of your msn/messenger federation partner (it will likely be “messenger” or “MSN”)
Remove-CsPublicProvider -Identity MSN (or messenger, depending on step above)
New-CsPublicProvider -Identity Skype -ProxyFqdn federation.messenger.msn.com -IconUrl “https://images.edge.messenger.live.com/Messenger_16x16.png” -VerificationLevel 2 -Enabled 1
Restart your lync client and check that Add Contact | Add contact not in my organision | Skype exists
now enjoy IM and audio calls between Lync and Skype…. video apparently coming soon.