Lumen:
In 3 you have to add a letter to the 3rd and last words (in the latter case making a Latin-style plural). You then have fodder for an anagram.
4 has an extra letter inserted in the first and 5th words. The clue is a reversed letters-in-other-letters to give an American spelling of a word for stink.
15 a letter is added to fourth and sixth words.
I'm not sure it's possible to work out what to do unless you have the book title and have read the Wiki piece on it. Encoding is perhaps slightly misleading as - if I've got it right - the letters in the columns simply move around.