There are a few free options:
1-I have a GoPro so I use GoPro studio. You can download for free right from the GoPro website. I believe all you need is your camera's S/N.
2-Microsoft Live Movie Maker (should come standard with windows 7/8/10 - if not you can download for free from Microsoft.com)
3-VSDC Free Video Editor from downloads.com (just make sure to uncheck the install boxes for the adware that comes with it)