Use the control buttons to control  the timeline view and to edit keyframes.

Use:             To:
             Zoom in by a factor of two.
             Zoom out by a factor of two.
              Add a keyframe to the selected property (or properties) at the current frame(Hotkey "Insert").
              Delete all keyframes of the selected property.
              Set current frame to next key  frame(Hotkey "Page Down").
              Set current frame to previews key frame(Hotkey "Page Up").