So, there are many solutions and also many interpretations of what you ask for 😊
I assume that you don’t have problems with getting a clip from your phone to the computer (and after that loading the clip into the media room), is it? (If it is the problem, then browser the internet for a number of solutions, including the one that lets you connect the phone to the PC and drag the clips into a folder etc.)
What I understand of your question is, that you have the clip from your phone available on the PC, but that you want parts of the entire clip selected and readily available into the media room, so that you can add them to the timeline at will.
If THAT is the question then a possible route is, to include the entire clip into the media room, then right click that clip and in the menu select the PRECUT tool. In the windows that is opened you can either select one part or multiple parts of the original clip. After you have clicked OK, the precut clips become available in the media room readily available for addition to the timeline.
See also:
https://help.cyberlink.com/stat/help/powerdirector/21/win/enu/98_01_05_how_to_trim.html?q=precut
Hope this helps.