Free?: Windows movie maker or some online shit... google free HD video editor its gonna suck tho compared to some of the free but illegal ones.
You have many choices when getting editing software.. I would recommend premier pro its a little more simple then sony vegas. you can always buy software if your in high school for cheap because the student discount but if you want to get it for free get find a video with alot of likes and comments how its working. title would be something like (get adobe premiere free crack or torrent) If you have apple get final cut pro instead.