The 22-year-old Irish midfielder signed a long-term deal with the Toffees on deadline day.
"It is a price tag and one I need to deal with," Sky Sports News quotes McCarthy as saying. "I am looking forward to trying to prove why I am here.
"It is not going to be easy, we have got a lot of competition for places. I am going to give it my best shot and hopefully I can do well."
McCarthy could make his Everton debut on Saturday when the team hosts Chelsea in the Premier League.