I don't understand your question. Could you please elaborate, giving more detail about what you're trying to do and what is happening?
If you're having trouble, it helps if you provide answers to the questions listed here: "FAQ: What information should I provide when asking a question on this forum?"
My first guess is that you are trying to playback using the space bar. After Effects doesn't work that way. Use the period (.) key on the numeric keypad or the Preview Panel to generate a ram preview. If you are getting slow playback with ram preview then your system is not up to the task of playing back a preview of that size. Reduce the composition window's resolution and scale.
My second guess, you shot at a high frame rate with the GoPro and have interpreted the footage at a lower frame rate. Come to think of it, this is a lousy guess because it assumes you have an understanding for footage interpretation, frame rates, and how AE handles previews.
Third guess, you have rendered a project to a lossless codec and it won't playback smoothly. That's normal for lossless codecs.
More information would help us .... ooh, never mind. You've heard that twice already.
Y'know, it really helps to lean the After Effects Basics before you decide to dive into the deep end of the pool. No kidding. Many people have tried to jump in feet first, and almost all fail.
So once you get AE reinstalled, go here first snf fight the impression you can do anything just because you have the software.