Scrubbing 

Click and drag the cursor around to move through the video footage.

You can also click the HH:MM:SS area on the scrubber to change it's mode from time to frames.

In/Out Points 

Note: You must left-click on the video, or have the video list active for keyboard shortcuts to work as expected. If in/out points aren't being set for you, click the movie you're editing. The video list (bottom of window) should become active and key shortcuts should then work.

You can press the I and O keys to set in and out points respectively.  You may also drag these using the handles provided, much like the QuickTime player.

I/O selections are useful. You can:

1. Process the selected I/O clip without having to create a separate sub clip to do so.
2. Create new clips (reference, or self contained).

The main reason that in/out points exist is to allow super fast processing of sub clips. Just set the I/O point and press the Process button.  Stomp will process only the portion of the movie defined by the in/out points.

You can also create two different types of movies from an in/out selection.

1. Right click on the scrubber bar to bring up the menu, you should see this:
2. Trim to Selection:  This will reduce the selected movie to its in/out selection.  You can undo this by pressing Cmd-Z.
3. Save Flattened As / and Add: Both of these options save a reference movie, which is a movie that refers to the existing content.  Reference movies are useful if you want to store a subclip of some movie and give it a name.  The "Save and Add..." option does the same thing (creates a reference movie) but also adds the new movie to the list of videos. 
   
   Note: The movie is also flattened during this process. Flattening will ensure that the movie is streamable from the web. 
4. Save Flattened Selection As / and add: These two items let you create full movies from the current in/out point.  The video is "copied" into the new movie and it becomes entirely self contained.  As with the above, the "and add" item will add the new self contained movie to the list of videos.
   
   Note: The movie is also flattened during this process. Flattening will ensure that the movie is streamable from the web.