The mp4 files (GoPro) are already on my computer. When I try to put them into a project...the audio runs smooth, but the video stops and jumps. I've watched those videos a thousand times with no issues on other programs. I really want this to work.
The problem is your computer is well below the minimum specification for handling HD video playback in MEP.
MEP is a non linear editor and renders the video as it is playing, if the processor is not fast enpough and has insufficient RAM then it cannot keep up in realtime, hence the stutter.
The minimum computer specification for HD video is here - note this is a minimum specification only and a faster processor and more RAM is highly recommended.