1. Sign in to Lync.
2. On the Contacts list, Find a contact of the person who you want to send an Instant Message.
3. Right click contacts and choose Send an Instant Message.
4. New window will appear and you can start send the message by typing message at the text box.
Note: To see my other blog post about Microsoft Lync 2010, click here. If you have a different or better way, please share with us.