When placing an element on the timeline (see: Add elements) or moving it along to reorganise elements (see: Organising elements), the click and drag method happens to be convenient but lacks of the precision you may require at certain times. If you need to place an element on a concrete frame, you will have to choose a different way making it possible to adjust the position through numeric parameters.
Defining entry and exit points of an element allows you to be specific about adjusting exactly the moment in which an element appears or disappears. Entry time and exit time parameters are established based on minutes, seconds and frames –following the standard code min:sec.fr– and are available to edit on the Properties panel of the element in question.
There is an alternative or complementary way to locate one or different elements being precise: the position marker (the blue bar on the timeline). This marker is particularly useful when you need to position a variety of elements in a same point. First, you use the marker to fix the desired exact position and then, any other element you bring closer –to the initial side as well as to the final side– will remain stuck to it as metal to a magnet. You can repeat the process as many times as you wish by moving the marker to any point of the timeline. Click on the button with the plus sign (+) next to the Timeline red cursor or the Show Marker button next to the Timeline controllers to place the marker.
Except for the Empty videos, the video clips are the only elements that can't have their end times modified, since it is not possible to change its length. By changing their start time you will be able to move it along the Timeline.