MASKING 

Firstly I imported two videos to Premier Pro. Here I added in points and out points to shorten my clips to lengths I wanted.

 

I applied a 'linear wipe' to the second clip which alowed me to cut it to about 40% and layer it ontop of my first clip. I then lined up the two clips and adjusted the brightness and contrast as the lighting changed while we were filming.

 

I deleted the audio and rendered all of the clips. I the exported it to quick time player. I then went on youtube and uploaded it.