To make a call to a number outside of your Directory, you can use the Dialpad in the Directory tab.
Click the Dialpad button in the left panel.
and then dial your number in the Dialpad in the right pane. The dial string is displayed above the Dialpad. Click the backspace icon to delete a digit or character.
When you are done, press Call to place the call.
Note: The Dialpad in the Directory tab is only for initiating new calls. If you want to "dial 1" within an existing call to initiate another call, use the Dialpad within a call option.