Starting the SFM
You can launch the SFM directly from Steam, as you would any other game. When you launch the SFM, you'll see a startup screen that you can use to open a recent session, create a new session, or browse to an existing session. Specify a name for your session and a directory to save it in, and click Create.
Loading a map
Before you can begin creating a movie, you have to load a map. Right-click in the viewport window, and then click Load Map. You'll get a list of maps available on your computer. You can filter this list by mod by typing text in the Mod Filter box at the top or by using the drop-down list. You can also filter by file name by typing text in the Filter box at the bottom. Choose the map you want, and click Open.
The SFM saves your movie as a .dmx file, which is your session. Inside each session, on the timeline, is the sequence, which contains a series of shots that make up your movie. Each shot contains a unique scene, which starts with a single Source engine–generated game map. As you play back your sequence, every time it plays a different shot, the scene for the old shot is unloaded and the scene for the new one is loaded. Each scene contains elements, such as cameras, lights, and models.