In your app dashboard, you'll find everything you need to get started.
The center pane is where you will do a bulk of your work. By default it shows your inbox contents and allows you to manage your recent calls, text messages, and search for older events. The center pane will also change to allow you to access any settings that need to be configured.
The right pane is your dialer. This phone dialer will use your computer's (or phone's) mic and speaker to make and receive calls from your phone numbers. You can also compose text message from the dialer pane.