I use two different editing programs, both are free. One is windows movie maker as mentioned above. The other is VSDC Free Video Editor. It's a whole lot more complicated, and I know I'm only using a sliver of its capability.
At the moment, I'm making gaming videos on the PS4, so I just use share factory
It is pretty basic and there are some limitations, but so far its the only piece of software that allows me to have multiple tracks on one video without plastering watermarks all over the place! Also you have the option to import your own images and music files and all the description/tagging is done though it! I would recommend it as a good starting place