I stored the evidence regarding Viet's political crime in the file.
Koichi scored a landslide victory at this election.
What should I do to finish the fight?
When you obtain something you need to keep it safe, so you decide to store it somewhere. Then you can always go back and look at the thing you managed to achieve, to score, or at least to finish, and no one can take it from you.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You haven't learned this reading yet so here's a mnemonic to help you:
You need to store all of the old saws (おさ). You were able to finish and to achieve everything you wanted with them, so it's time to put them away so they'll be safe.