You will need to download a video software editing tool. Here are a couple of free ones. One is for Windows Devices (Windows Movie Maker) and the other is for Apple Devices (iMovie).
Windows Movie Maker
- Click Add Videos and Photos. Browse for your file. It will appear in the right part of the window. This is your timeline, also known as a Storyboard
- Find the section you want to separate the clip
- Click Edit > Video Tools > Editing > Split
- Select clip to Export
- Click the Project tab (the icon to the left of the Home tab) > Save Movie
- Select For Computer, enter your Filename and click Save
- Click File > Import > Movies. Browse for the file you need. Then, click Open
- The file will load in the Event Window on the bottom screen of iMovie.
- In the Event Window, select the portion of the video you want to isolate as your first video clip and move it to the Project Window
- Click Share > Export
- Select the quality of the video and Export
- Delete the clip from the Project Window