Hello SamYT. It seems like You don't understand what Replay Mod do. I suggest reading Replay Mod official documentation. But i will try to explain how does it work. When You join the world, mod start to record everything and store it in .mcpr file. Then when You leave Your world it save it on Your computer. If You want to make a video, You need to render camera patch in the Replay Viewer (it is explained in the documentation). After that You will have a video ready to edit on Your computer. Making videos is not a paid feature.