Drag an effect on it and a box with a timeline at the bottom will appear:


Drag the slider to the point where you want the effect to start, along with the diamond at the start so they are at the same point. Make sure the bar for the effect is at 0:


Where you want the effect to peak and be most visible, drag the slider on the timeline to this point and make the effect bar go up to any value you want, whichever looks best. You will notice another diamond has been made, this is called a keyframe. They determine what happes and at which point on the timeline of the clip:


Where you want the effect to end, drag the slider on the timeline to the desired place and drag the effect slider down to zero again:


Voilс, effect placed.