Hover over a clip in the timeline and click the ‘edit shot’ button. This will open the edit clip window where you can adjust the clip length by dragging the in/out arrows on the blue bar below the clip preview. You can also click in the middle of the bar to move to a different section of the clip whilst maintaining the same clip length.
TIP: After clicking the in/out arrows you can use the arrow keys on your keyboard for more precise adjustment.