Some would call this the nitty-gritty of the import operation. This is where the action takes place after all. You've set your parameters and video options and you are ready to import.
If you chose to "Import the entire videotape to my computer," then the preview is already playing, and Windows Movie Maker is capturing. If you haven't hit Play on your source device, you're just wasting precious storage space on nothing. Feel free to use the "Stop importing after (min):" option to set how long the video should be and forget about it as you do something else... or just watch it while it's being imported. Windows Movie Maker will automatically stop importing after that amount of time has passed, or you run out of hard drive space. Capturing video takes a lot of storage space, so be sure to have that covered.
If you chose to "Only import parts of the video to my computer", then the preview isn't running, Windows Movie Maker isn't capturing yet, and you are afforded the time to seek out the part of the video you really care to import.
Now, pay attention to the Preview Window and the "Digital Video Camera controls:"
Windows isn't actually controlling your analog device through this, but if you have hit Play on your VHS (of any other analog device hooked up via the capture device) and you see nothing on the preview window, it's because you have not hit Play on these controls. They basically control the playback of the Preview Window. Make sure it's playing before you begin capturing. It will also need to be playing as you seek within your video for the section where you want to begin capturing. Once ready, click to "Start Video Import" button to begin the operation. The "Start Video Import" button will turn into the "Stop Video Import" button then. You will want to click that when you're done. Then, you can click on "Start Video Import" again if you wish to navigate to another point in the tape to begin capturing. When you're done grabbing your clips, simply click on "Finish".