I asked about extra boards because the packages folder is where the extra board files are located. You don't have any which presumably explains why you don't have the folder
As to the video, I started to watch it but not for long. If I wanted to use the whole of the memory available on a Nano I would delete the bootloader by overwriting it by programming the Nano with a programmer or another Arduino
Presumably you have a reason for wanting more memory. Are you sure that your sketch is using memory as efficiently as possible ?
Why not post it here for advice ?