To add a transition from one clip to another, first move the Playhead to the point between two clips on the Timeine.

Then click on the Trans button in the button bar at the bottom of the Shelf area on the right.

In the window that appears, you'll see a box listing the different types of transitions (each of which has a blue icon).

Select the transition you want, such as a Cross Dissolve. A preview of the transition will play when you click on it so you can see how one clip fades into the next clip using this particular transition. Or you can click on the Preview button to see the clips with the transition play in the Monitor to the left.

You can also adjust the speed of the transition - how quickly one clip will transform into the next - by dragging the button on the Speed slider bar. Drag to the left to make the transition faster, to the right to make the transition slower.

For some transitions, you also can use the little wheel to adjust the direction of a particular transition (click on the Push transition, for example, to see how you can adjust the direction of the transition using the wheel).

When you're done with your selections, click on the blue icon for your transition, drag it down to the Viewer and position it between the two clips where you want to create a transition (such as where you placed the Playhead above). Release it and you'll notice that a blue transition clip has appeared in the Viewer between your two video clips.

You'll also see a red line appear under the clip, with the red area moving slowly to the right. When transitions are added, the affected video must be regenerated, or rendered.

This red line shows the progress of the rendering process. It may take a few moments for the rendering to complete (particularly if you selected a long transition between clips, which will take a longer time to render).

When the rendering is done, you can move the Playhead to the first clip, click outside of the Viewer Timeline and then click on the play button to see your movie play, with the first clip now transitioning into the next.

You add additional transitions between other clips in the same way.

To remove a transition, simply click on it and press the delete key on your keyboard.