Welcome to Squidboards! Now, I cannot say I personally play wiper, but I currently coach a LUTI D9 team that has a wiper player.
Wiper’s purpose is to distract and kite the enemy around in as annoying of a matter as possible. You basically want to be a big annoying buzzing fly that‘s super mobile, threatens damage from fairly safe/somewhat risky positions, and be able to create openings for your team in this way. Despite this, I would say it is somewhat of a harder weapon and role to fulfill than, say, a Splattershot. You need to have good understanding of your spacing and what areas of the map are available for you to take and threaten versus what is too risky to do, even as a wiper.
Of course, everyone’s playstyles differ and your mileage may vary. It’s hard to tell you what directly to improve if no one’s seen your gameplay before. Do you use the Replay Code feature? Please post your Replay Codes here so people can directly see your gameplay and we can tell you what you did great on and what needs a little adjustment :) Good luck getting out of A+!