Facebook say H.264 videos that are no bigger than 1280x720 at 30fps are best for it.
For straight conversion of videos get Handbrake,
* load in your video
* select high profile preset
* tick the box for web optimized
* on the picture tab make sure under size that width does not exceed 1280, if video is smaller than nothing needs to be done
* on the video tab Framerate (FPS) should be set to 30
* click start to begin encoding then once it is finished upload the video to Facebook.
You can save those settings as a preset by clicking the add button.
Handbrake is not an editor, if you want to edit the videos your going to have to use other software.