“Just try to have fun with it... Just don't overthink it," the 50-year-old actress told Extra on Thursday.
Since signing up for the platform on Oct. 15, Aniston garnered 18.9 million followers and even broke Instagram's and Guinness' world record for reaching 1 million followers in five hours.
Her first post -- a selfie with all of her former "Friends" costars -- earned more than 15 million likes.
Meanwhile, McConaughey joined Instagram earlier this week, and also marked his 50th birthday. He had more than 1.5 million followers as of Friday night.
For his first post, the "Dallas Buyers Club" star shared a video in which he opens up about joining social media. It received more than 2 million views.
When it was suggested that Aniston inspired McConaughey to join Instagram, the "Murder Mystery" star responded: “Did I inspire Matthew? I have now achieved some very incredible things, people."