The Poland international completed his move from Borussia Dortmund to the Allianz Arena earlier this month, having agreeing the switch in November.
After four successful years at Signal Iduna Park, he will likely the lead the line for Bayern as they target a third successive Bundesliga title.
Lewandowski scored on his Bayern debut against Duisburg, but Guardiola will not put any pressure on the striker to fire from the off when competitive action gets under way.
"Maybe he will need some time but he has the quality, he did everything to come to this club," Guardiola said on Thursday.
"I am here to support him. He will have the opportunity to have a good life with his family over here in Munich. The rest will come by itself [but] we'll need time, a change like this is never easy.
"He'll need time - and he'll get time."
Having lifted the DFB-Pokal and overseeing a record-breaking Bundesliga-winning season, Guardiola believes he will face a challenge this season in ensuring his squad remain hungry for silverware.
"If you won some [titles] you are a little bit more loose and relaxed," he added.
"That's the challenge for a coach - and it's a big challenge. We have to maintain the level of the last year with this team.
"That's going to be quite difficult as a lot of important players were at the World Cup. It's a huge challenge - but I want to take it."
