You are WHITE, and this is the very position you won as black two boards ago — feel it from the other side. Black's chain has two junctions: (7,6) is simultaneously the column-7 three's fourth stone and the spark the row-6 pair needs, while (8,6) is the square that would complete the open four from the other end. One white stone on either junction breaks the chain before the first four is ever played — the cheapest defense in gomoku. Take one now; after black's four lands, junctions stop being yours to take.
Finish this step to move on.