My explanation from making a bit of edits:
Pause the replay at the beginning frame, press "2" for a free camera (with the free camera, you move it up down left right and forward with W A S D, and you can move where you look by holding down the right mouse button and moving the mouse), every 100-175 frames you should make a keyframe with "K", (moving the camera around the enviroment, and make sure you don't clip through the ground or tori/uke). After viewing the replay and if you like it, then make sure to save the replay or the keyframes wont save to your replay.
Pressing "I" messes up the replay for me, so I don't know if it works for you
Take care, friend.