Scenes
Movies tell stories by a series of scenes. A scene is a sequence of action (actors doing stuff or scenery moving by) and dialog (actors talking). We see a scene in which something happens in our story. Another scene of action and/or dialog follows in which something else occurs advancing the story, and so on.
So let's write our first scene. Since we have an outline, we already know what's in it.
To make writing easy, I like to have my outline handy in Celtx also. If your outline is not open, just double-click on it in the Project Library and it will open in the main script window, as shown in the following screenshot:
Now that we have tabs for the screenplay (currently hidden), and for the outline (now showing), it's easy to switch back and forth between script and outline by just left-clicking on the tabs.
We start the scene with a scene heading (also sometimes called a slugline). Celtx will format this for you (scene headings are always in ALL CAPS). Just select Scene Heading from...