The Dockers had never won back-to-back finals in their 19-year existence prior to Saturday's 25-point win over the Sydney Swans and the players were shell-shocked at the thought of playing in a premiership decider.
"I just spoke about it with Michael Walters and we can't believe it," Johnson said.
"It's a big achievement. We're the first team to make the Grand Final for the Fremantle footy club and we're just going to take it in as the week goes on.
"We'll make sure we stay on the right track, not let anything interfere with us and make sure we enjoy the week and go out there and show the AFL that we can match it with the best."
Coach Ross Lyon spoke to his players behind closed doors immediately after the win.
"There was a few things later in the game that slipped away and he just wanted to make sure that we need to go to the end of the game," Johnson said.
"But he also said enjoy the week, enjoy it with the family because it doesn't come too often.
"We might not play another one for a number of years, so make sure we enjoy it."
Johnson believes the Dockers crowd lifted his team against the Swans. The 43,249-strong crowd was the second largest the Dockers have played in front of at Patersons Stadium.
"They're awesome," Johnson said of Fremantle's fans.
"They've been waiting for a long time since we started and hopefully they can get out and celebrate and get right into it.
"Hopefully we can get a really good group over to Melbourne and hopefully they get amongst it and enjoy it."
Johnson was also humbled to be named All Australian for the first time on Monday night.
"It was a surreal feeling," Johnson said.
"I was sitting on the couch when I found out. It was just weird sitting there when your name gets called out.
"It's an honour to be part of an elite group like that, but I want to give a special thanks to my teammates for helping me along this year and also the coaches."
