Jackson Irvine, Awer Mabil and teenager Garang Kuol were on target as Arnold handed debuts to Aiden O'Neill and Alex Robertson in his team's first appearance at home since losing to eventual World Cup winners Argentina in the last 16 in December.
"Let's not get carried away, because these kids need a heap of experience and plenty of game time at their clubs," Arnold said after the win at Western Sydney Stadium.
"The senior boys are doing it every week and you can see the example that they're setting to the young ones.
"But, as I've said many times, I believe in Australian talent and the Australian mentality within those kids, it's just about them getting the opportunity and the chance.
"That's about the fourth friendly I've had since I've been in charge and it was an opportunity to put some young kids in and around the older players and let them lead the way."
In front of a modest crowd of 20,668, Irvine put Australia ahead and Mabil restored the Socceroos' lead after Felix Torres had equalised for the Ecuadorians.
Kuol, the striker who burst onto the Socceroos scene in the build-up to the World Cup, bundled home the third from close range with six minutes left to score the first goal of his international career.
"It's a learning experience for these young kids," said Arnold, who remained coy about handing another promising teenager, Nestroy Irankunda, his debut in a second meeting with Ecuador in Melbourne on Tuesday.
"You're playing against quality players from South America and those kids haven't played against South American teams before.
"I was very happy with young Alex and Aiden O'Neill, I thought, was very, very good.
"These young boys are tapping the older boys on the shoulder."
