The volume and speed controls are located at the top of the screen on the Home tab.

Additionally there is a slider bar that appears above the playback controls, this is the Playback position of the dictation.  The playback position can be moved by clicking and dragging the indicator, or playback position can be adjusted incrementally with the Fast Forward and Rewind controls or foot pedal.

Use the selection arrow to the right of the setting display to open the selection menu.

For Volume, select Louder or Softer to adjust incrementally, or directly select the desired volume percentage.

For Playback Rate,  select Increase or Decrease Speed to adjust incrementally, or directly select the desired playback rate.  Additionally the Hotkeys to Increase Speed (CTRL+T) and Decrease Speed (CTRL+E) are available.