The attacking midfielder has joined the Blues from Aston Villa this week.
Kellyman told the club's website: "I think one of my key characteristics is my confidence. The more confident I feel, the more successful I have been.
"Whether that be coming into new environments and meeting new people or on a football pitch – showing people what I can do and what I am about – I think my confidence has helped me be more successful."
Kellyman admits Chelsea's focus on youth was an attraction.
He added, "That was a big attraction for me.
"I have seen young players stepping into the team and playing week in, week out, in the Premier League and I feel like I will be able to take my opportunity as and when it comes.
"I want to be successful in the Chelsea shirt; to win games and hopefully trophies. (Over time) hopefully, I can become one of the faces on the side of the stadium. I want to become a big player for this club."