Directories -> Call History
The Call History window is accessed from the History tab or from the tray icon menu. As well as reviewing recent activity, you can dial someone from here by clicking on their telephone number. It's good practice to store the names of people when you speak to them, especially if you're likely to speak to them again.
By default, the Call History screen returns the fifty most recent calls.
Also, to aid readability you can hide and show individual days from your history by pressing the expand/collapse button to the left of the date.