You can do so much more with Final cut express than you can compare to iMovie, refining more imaging and better effects as well as dual pictures and different screening options.
To use Final cut express you use the up and down arrows to get to prior or later clips and when refining to frames you use the left and right arrows all found on the keypad.
You can also cut parts out of clips similarly to iMovie but instead when going through the clip and splitting you use the i character to start the clip from where you want and the o key for out which finish the clip cutting the remaining clip out when you have done this to insert the clip int your project you double click the clip and drag onto the right screen in the 'overwrite' section.
When refining clips further and more accuratley use the left and right arrow to move through each frame on the timeline. Then, use the 'razorblade' tool on the bottom right to remove then select shift and backspace after highlighting by double clicking. Final cut setup----->
To add audio select file>open>add audio>then drag and drop the selected file into the clip.
click motion at the top of the left screen for effect of dual imagery.
You can select blur or stylus etc to add further effects although some effects on a clip may need to be rendered by selecting sequence >render>all>both.