When Montag goes to Faber's house, he is seeking for the answers to why books are so important and necessary. Faber tells him that books are important for three reasons: quality, leisure, and motivation to act. But, he is a bit dejected because he feels that in their society, there isn't much that they can do to change the system, and bring books back. He figures the only way to really succeed is if "the fireman structure itself could be burnt." He says that way to do that is to
"print extra books and arrange to have them hidden in firemen's houses all over the country."
Then, they could call in the alarm on these men, and all of the firemen's houses would be burnt to the ground, because they had books in them. That would start to undermine the system, throw everyone for a loop, and give Montag and Faber time to distribute other books, and start the wheels of change. And, it just so happens that Montag has "a list of firemen's residences everywhere" and Faber knows an "unemployed printer" who could start printing off the books for them to plant. So, that's the plan they start with; print some books, plant them in firemen's houses, call in the alarm on them, and watch the homes burn. I hope that helps; good luck!