If you want to alter the speed a video clip plays, which is to say make it go faster or slower, put the video into an open space in the Timeline. You can put it at the very end of an existing sequence where it has space on either side, or create a completely new sequence just for altering this clip. Double click on the clip and then go to Modify in the task bar and then down to Speed. A window will come up so you can numerically change the speed of the clip. If you want the clip to go slower you will change the percentage to be less than %100, and if you want it to go faster than it originally was then you change it to be higher than %100. For example, if you want it to go half speed you will change it to %50, and if you want it to go double speed you would change it to %200. The length of the clip in the Timeline will then change to match the length the clip is after this alteration.