To replay a previously recorded journey select Tools/GPS/Replay GPS from the menu. The Open File dialog will pop up which will let you select a file containing a recorded journey.
The replay will begin immediately. The replay controls appear on the right of the output pane.
The slider at the top controls the replay position, the left being the beginning and the end on the right. You can move to jump to positions in the replay.
Click the two buttons below the slider to pause or end the replay.
To change the replay speed go to Settings/GPS/Replay.