Breaking a video into clips

[Leap4artnc]

I am so lost! 

I am an artist and am putting teeny videos into Instagram. 

I shot a video on my iphone showing me taking a bad painting in alcohol ink into something nice. It is about five minutes. 

How do I break this five minutes into clips to edit the clips. Everything I have tried makes the the rest of the video disappear. 

I am watching the videos in the how to do this. 

Thanks for any help. 

Tommy @Leap4artnc