The young Magpies secured their spot in the final after an impressive away win against Leeds United last month and will face the Toffees at Goodison Park (kick-off 7pm BST).
Newcastle are also chasing promotion to Premier League 2 Division One, with Ben Dawson's side defeating Reading on penalties in their play-off semi-final and Longstaff is relishing the opportunity of playing in his first of two major finals with the squad.
Longstaff told nufc.co.uk: "Everyone is really looking forward to it. You play the full season to get to finals and we have the chance to go and win one so I think everybody is buzzing for it.
"On the back of the way we won on Friday night (against Reading) everyone is ready to go. Every chance you get to play in a cup final, you want to try and seize the moment and we'll try to do that on the night.
"It's a tough cup to get through to the final. I think we've done really well this year, especially as a squad, and everyone has played their part. We've done so well to get to this point and we want to go on and win the trophy.
"I think you just try and treat it like any other match but, obviously, it's a bit harder to do knowing what is at stake and knowing it's a final. However, we'll go in with the normal mentality of wanting to win and do things right and hopefully it will help on the night.
"We know Everton will be a good side. They've just won the top league (Premier League 2 Division One) and if you're not a good team, you don't win it. However, the biggest thing for us is concentrating on ourselves and making sure we do the right things.
"If we do what we've been doing all season, we'll hopefully be able to perform on the night and be able to win the cup."
United's second-string have enjoyed a terrific campaign this term, reaching the Checkatrade Trophy knockout stages along with achieving their highest points tally since the formation of Premier League 2 in 2012.
Longstaff, one of five players approaching their first full year with the under-23s, admitted the togetherness of the squad has been paramount to the young side exceeding expectations.
Longstaff added: "The biggest thing is that we're a young side. At the start of the season, I don't people expected us to do so well. We have a few older players in there, such as Owen Bailey. He is one of the senior members in the group now when, last year, he was one of the younger players.
"I think it has helped having players from last season who have put us right and looked out for us. The younger ones have also come in with lots of energy and hunger to do well, which is a good mix and has helped massively throughout the season.
"This is one of the closest groups I have been with. Everyone gets on well and we all bounce off each other. To win a cup with the group, after battling through a year of ups and downs would be a big achievement."
