Seems like a solid project, but I can't fathom how one can possibly hope to create a scalable distributed network that can handle bulky media network traffic while also promising anonymity. People usually have a hard enough time tackling those problems separately.
Everything is explained in the whitepaper, they worked out the theory behind it and there is also some pseudo code. You can see they just didn't woke up in the morning, hacked up a whitepaper with some feature would appeal people with cash in their pocket and started this.
File transfer is described in chapter 6 of the whitepaper. Simply said they will leverage existing distributed file systems like
or IPFS I suppose. If you think they are limited to a few megabytes, check this out