The 19-year-old made his debut as a second-half substitute in September's World Cup qualifier against Moldova after a surprise call-up by Roy Hodgson.
It remains his only cap so far - having been fast-tracked from the Under-21s for whom he made just five appearances - although Barkley is tipped to start in Friday's Wembley friendly against Chile.
"It was a nice surprise to be selected (in September's squad)," he said.
"The first two days I'd say there were a lot of nerves but then it settled because it felt like I was meant to be there.
"It's helpful being around different players that I'm not used to - being around big-name players - it's good just talking to them and seeing the way they approach games. It bodes well for future games for me.
"It was unfortunate I just missed out on a goal but it's always good playing for your country.
"To come on for the seniors was a great feeling and a good moment for my family as well."
Despite his youth, both in age and experience, Barkley admits he has dreamed of going to a World Cup, although he insists performing for his club has to take precedence.
"It's every youngster's dream to play in the World Cup," he told evertontv.
"But I'm not really thinking about it at the moment - hopefully if I play well for Everton then I will push into that team and get to Brazil."
Barkley has emerged as a key performer in Everton's good start to the season.
That he has been so involved is largely down to the faith put in him by Martinez, who has given him an attacking role in an advanced midfield position.
"He's given me a lot of freedom, he believes in me," added Barkley.
"It's good because he's put the belief into all of the players and we're all playing well.
"He wants me to be an all-round player, and to be able to play in lots of different positions.
"He's spoken to me a lot about stuff like that and tactical ways of the game."
Barkley scored his first Premier League goals of his career against Norwich and Newcastle this season but he is targeting more this term.
"With the players around me like Steven Pienaar, (Leighton) Baines, Romelu Lukaku, Kevin Mirallas, you're always going to get chances," the teenager said.
"I'm happy with my two goals but I feel like I could have scored a few more.
"I've set myself goals. It would be good to get double figures in my first full season in the Premier League but any more is a bonus."
- Sports & Recreation