This trophy requires you to land 5 hits on an airborne enemy. As enemies do not really jump, you will need to find a way to make them airborne. There are numerous skills throughout the game that enable you to do this with various weapons, but early on the Longsword is a good choice for this.
Use an attack that knocks your enemy in the air (preferably a tougher enemy so they don't die too quickly) then quickly switch to a secondary weapon like a bow, or daggers or faeblades. A bow is the easiest as you simply need to shoot the target 5 times and this trophy should unlock a few seconds later.