Did I correctly describe the work of this cryptor?

Question

Cryptography

In general, I'm trying to understand how cryptors work, I found this video on YouTube.
https://www.youtube.com/watch?v=2fV2jfd5usg&t=2s
In it, the author takes njRat (Remote Access Virus) and encrypts it.
The question is, did I understand how it works?
Cryptor generates random DLL files which are not present.
Then he added a string for decryption, or xs it's a simple Maby key to get attention.
Further, as far as I understood, he specially made a form (supposedly games).
Only it is not clear how his software takes njRat ?. Or he takes it, encrypts it (the whole code) and then inserts it into a string (it's a mystery to me), answer who fumbles. But I think that this is the only solution where the virus code comes from.
P\S The author has all the sources under the video.