The former Schalke boss replaced Thomas Schneider on Sunday, with Stuttgart level on points with Hamburg – who are in the Bundesliga's relegation play-off spot – after a nine-game winless league run.
Stevens is aware of the challenge ahead of his team but said the only priority was staying in the top flight.
"I know it's a challenge but I'm up for it," he said ahead of his side's trip to Werder Bremen on Saturday.
"As soon as I heard from Stuttgart, I didn't need long to say yes. I felt ready. There's going to be an incredible amount of work to do in the coming games and I'm going to talk a lot to the players.
"Our only priority now is to stay up and we need to focus all of our efforts into that. We need to be united."
Stuttgart have scored the equal ninth most goals (38) in the league but their defence has been the problem.
They have conceded 51 times in 24 matches to hold the third worst defensive record in the league.
Stevens said his side needed to work for one another but knows how tough it will be against 11th-placed Bremen, who are unbeaten in their past four league matches.
"We must defend and attack as a unit," Stevens said.
"I'm getting to know the team better with each passing hour. I talk to each and every individual. Now we just need to come to the right conclusions. It's important that the players help one another.
"I hope I can put out a solid side at the weekend. Bremen take risks, are well organised and have shown themselves to be very stable of late."
Bremen striker Franco Di Santo said his team were likely to continue with a 4-4-2 formation, with the Argentine alongside Nils Petersen up front.
"Playing off Nils is working well – not just for me but for the whole team as well," he said.
"If the results are right then you won't hear anyone complaining about the system but I certainly feel very comfortable in this formation. I've just felt really good in the last four matches."
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