Clue 1)Miss Scarlet was in the Library, but she didn't have the knife.
Clue 2)The six suspects are : the one with the candelstick (1), the one in the Library(2), the one with the Lead Pipe(3), the one with the Pistol(4), the one with the Rope(5), and Mr. Green(6).
We know that Miss Scarlet is in the Library, so where "Library" and "Miss Scarlet" intersect, we make a green dot. She did not have the knife, so where "Knife" and "Miss Scarlet" intersect, we make a red dot.
Since all six suspects are different people, then none of the six suspects can have the same things. The one in the Library(2) cannot have the Lead Pipe, because that is (3). Neither can it have the Candelstick, Pistol, or Rope. Mr. Green cannot be in the Library, because he is (6) and Library is (2). He also cannot have the above mentioned weapons.