You do not necessarily need to convert the whole video if you need only part of it. Moreover, it is better to try and see the result of so to speak "test conversion": when you choose a small part of a movie and convert it into the selected format. After that if you are satisfied with the output and made sure you can playback it on the chosen device you can convert the whole movie with the same settings or change the settings if you see something wrong. Partial conversion is also useful when you want to cut the scenes from the movie or select only a part of a movie, for instance a music video clip.

Use the mouse cursor on the slider to select a part of the video to be converted. Select the beginning of the video with the mouse cursor (it will turn into a double sided arrow), click it and, without releasing, drag to the place where you want the episode of your video to begin. The same way the episode end is selected:

You will see the hint, showing the selection beginning and end time and the selection range. You can use it to adjust the settings.

After you select the necessary range, click the Start Conversion button to begin the conversion process.