Extract a portion of a video to a separate file

First you want to make sure the Sequence Settings are correct, meaning they match the source video clip. Import the clip into Project Bin, then right click and select New Sequence from Clip. Alternately, drag the clip to an empty timeline and drop it, and a pop-up should ask if you want the Sequence to match the clip, say Yes.

Now you can trim the video clip in the timeline. Grab ends of clip with mouse and drag to shorten both ends down to just the portion you want to keep. Drag entire clip to far left, so there is no dead space preceding video clip. When you are satisfied with your editing, go to File > Export > Media

The default export settings are usually H.264 with a preset of Match Source - High Bitrate. Since this is for a PowerPoint, Medium Bitrate might be a better solution. This will create a smaller .mp4 file which is pretty universally playable on Mac or PC in most any player usually.

Typically, and especially as an inexperienced user, you will not change any parameters, other than setting the file name and destination for the export. Please see photo and look at Source and Export settings - you will both are 1920x1080, 29.97fps which matches the example source clip. Matching is usually what we want - if they don't match it could be a problem to look into. You will also set the Filename/Destination here by clicking on the current filename to change.

As I don't know what your source clip is, it may have different settings than my example, but again both parts should match. An exception example is maybe your source is 4K video, which is too big for a PowerPoint, so then perhaps you select a different Preset to export to, such as 1080p or 720p to make the video smaller. In that case, maybe just use a YouTube 1080p preset for example, sticking with H.264 as the Format.

These are general guidelines and not hard and fast rules, as every situation will differ, but this should get you going without much trouble.

Thanks

Jeff