Highlight the white text inside the block for hints ranging from vague to specific...
The clues may be confusing. One thing they do not make explicit is that the round wheels are spaces (no letters go there).
Once everything is filled in, it will read as a quotation from top to bottom and left to right. Use this to your advantage to fill in adjacent words.
The letters in the below groups are distinct "words" that will all be used in the same 4x4 section.
The "words" in the below sections are sorted by length, which makes for easy scanning.
Break down each of the 16 sections into groups, e.g. the first one has 4 words: 3 letter, 4 letter, 3 letter, 4 letter. So you need to use a grouping below of 3,3,4,4.
Big hint: only one of the sections has 5 spaces, so it is the only one to only need 11 letters - you should start with this one.
Final quote (punctuation inserted):
The demoniac person thinks So much wealth do I have today; I will gain more according in my schemes; I am the lord of everything; I am perfect; There is none so powerful and happy as I am. In this way such persons are deluded by ignorance and fall down to hell.