Arsenal had started the Premier League season with 2-0 defeats to both Brentford and Chelsea, with a clash with champions Manchester City to come on Saturday.
Having missed out on European qualification, the Gunners were thrust into the early stages of the League Cup but found their goalscoring touch in a morale-boosting win.
Pierre-Emerick Aubameyang netted a hat-trick leading the way with two first-half goals as Arsenal opened up a 3-0 half-time lead, with Nicolas Pepe netting shortly prior to the interval.
Bukayo Saka and Alexander Lacazette, just back from COVID-19, also scored in an emphatic display against the Baggies, who were relegated form the Premier League last term and are one of the favourites for promotion this season.
“When you lose a game, you have to win as quickly as possible,” Arteta said. “Todays match is going to give us some confidence.
“We had some players playing their first minutes - for example Auba - so to get some minutes and score three goals is going to be great for his confidence. Overall I think (it was) a really positive night.”
Aubayemang’s hat-trick comes after he missed the Brentford match after testing positive to COVID-19, as well as having been linked with a move away from Arsenal.
“I said at the beginning (that) the leadership, the solutions and the tools to win football matches has to come from the senior players,” Arteta said.
“The rest has to be complemented to that with the energy, the vibe and the passion that they bring to the group, and not the opposite way around. I think tonight was a good example.”