If the problem says "if x is true, then y must be true," that is already an implication. You can add the edge → y directly to the graph. No need to convert to a clause first, though you can write it as "NOT x OR y" if you prefer.
If the problem says "if x is true, then y must be false," add edge → NOT y. These direct implications are the building blocks of the implication graph. They show up in dependency constraints.