This link answers frequently asked questions about using Skype for Business, including updating from Lync to Skype for Business.
Skype For Business - Send an IM
This link provides steps on how to send an Instand Message in Skype for Business.
FAQ about Skype for Business (Lync) contacts
This link provides answers to questions that most frequently come up when dealing with contacts.
FAQ about presence and pictures in Skype for Business (Lync)
This FAQ provides answers to questions that most frequently come up when dealing with presence and pictures of contacts in Skype for Business (Lync).