The Toffees face their Serie A opponents after losing 3-0 to Spurs at Goodison Park last Saturday, and Koeman has called for a reaction from his players.
"Of course, after the weekend we need to react," the Dutchman told the club's website.
"The second half was not what we expect from ourselves. But the nicest part of football is that if you lose a game – if you are not happy with the performance – you get another opportunity in a few days and can show your reaction."
Koeman continued: "We will try to dominate the game – our intention is to play offensive football, to create opportunities, to score and we need to counter the strengths of Atalanta.
"For every football club, it is really important to be part of Europe. Let's hope for a good game and that the journey will take us a long way in European football."
Everton's opening European game is followed on Sunday by a crunch Premier League meeting with Manchester United at Old Trafford.