AARONCELLO'S PROFILE

Hiya, I need assistance in how to use Yanfly's Party engine's add-on, the "Party Swap Fix".
What it says on their page is "If you want to use the script call $game_party.swap_order(n,n)" and then it links you to this chunk of script:
Now! My main question is, where do I post these chunks of script and how do I get it to work? I've tried using $game_party.swap_order(1,2) in a script call, but it keeps telling me there's a problem in the "nil to integer" thing?? Help.

Alright, so my game has two protagonists, obviously the one that is in the first slot of the party is taken as the party's "leader" and then when they win a battle, it says "X's Party was victorious!"

I want to have it so the message will "The Party was victorious!"/"You were victorious!" (for when there's only one player in the party) instead of only naming the party leader.. This story is lead by the both of them and it's important that the game's messages reflect both players. I suppose the latter would be the better option because there are moments in my game in which you play as only one of the two protagonists.

I've looked at the scripts, haven't changed anything just to be safe, but I can't figure out how to change the wording. Thoughts?