Partey signed for the Gunners on deadline day after Arsenal triggered his £45million release clause.
He put pen to paper on a four-year deal believed to be worth £250,000-a-week as Mikel Arteta strengthened his midfield.
Arsenal were believed to be tracking the Ghana international for six months before they finally lured him to the Emirates.
Partey believes he will be given more freedom under Arteta than he was under Diego Simeone, according to the Guardian.
Partey was viewed as a holding player in a regimented system by Simeone and he felt he could add more.
While Arteta will also use him at the base of the midfield, he expects that he will be given more of an opportunity to showcase his range of passing and driving runs from deep.
Partey sent an emotional farewell message to his former club after completing his move to Arsenal.
‘Dear Atletico fans, today I only have words of gratitude for you,’ Partey posted on Instagram on Tuesday morning.
‘I want to thank the club for the trust placed in me from day one, but above all, I want to thank you, this wonderful fanbase that accepted me from the first moment and one that never stops believing in both the good and the bad times.
‘Atletico Madrid is not just a club, it is a family. Thank you.’