Answer
Via the messages area:
- In the left navigation click Messages.
- Click the pencil icon (New) on top of your screen and select the contact you want to write to. Use the search box to find a specific contact.
- Now write your message in the field at the bottom right corner of the screen and click on Send.
Via the contact list:
- Click Your network in the left navigation and find the contact you'd like to write a message to in your contact list.
- Click on the Send message icon next to the name of the contact.