The former Atalanta star joined Atletico on deadline day, penning a contract to 2030.
At his presentation, Lookman said: "For me, it's a blessing to be here. I'm very happy and content. It's fantastic to be here. It's a great responsibility to represent my country, but also a pleasure to wear the colours of such a special club as Atlético. So I'm incredibly proud.
"It's been fantastic to be here with the team, they've given me a great welcome, looking forward to sharing more training sessions with them.
"I am happy to be at this club and in this league, which is very important."
Asked what he will bring to Atletico, Lookman was enthusiastic.
He continued: "My game is very dynamic, it relies heavily on speed. I'm going to try to make a difference in critical moments. That's what I like to do. To contribute to the teams I join.
"I'm a team player, and if I can help the team, that's the main thing."
On coach Diego Simeone, Lookman added: "We had a good conversation before I arrived. It's fantastic to be able to talk to the person you're going to be working with."