HitFilm Express is a free Visual effect software for Windows. It is one of the easiest to use software, as it has well-organized menus to give access to desired options.
As you launch this software, it lets you choose from Start Compositing and Start Editing options. You should choose Start Compositing option, but you can go with either option as later you can access other required options to add visual effects.
After importing desired videos, images, and other media files, you can visualize the video in the Viewer window. It lets you add new composite shots to the added video. To do so, you can specify width, height, frame rate, aspect ratio, etc. parameters for the shot. It comes with some built-in visual effects including Light & Flares, Transitions, warp, Color correction, color grading, Quick 3D, etc. Using Quick 3D option, you can add bonfire, fluffy clouds, missile smoke, sci-fi shockwave, storm cloud, etc. visual effects to the video.
Additionally, it also has Keying options available in Effects menu. From here, you can access Matte Enhancement, Chroma UV Blur, Luminance Key, etc.
When you are done with adding VFX effects, you can switch to Export menu to save the processed video to Facebook, YouTube, Vimeo, etc. compatible platforms.