Victory over Sheffield United left the Glovers 90 minutes away from promotion to the second tier just 10 years after they were promoted to the Football League for the first time.
And the former Bristol City boss knows his side need to focus on the match and not get caught up in the hype surrounding a final at the home of English football.
"What you can't do is go there as a tourist," he said. "You have to go there as a professional footballer that has a job to do. We'll do the touristy things on Friday when we go down there to acclimatise.
"I'll get them in their positions and help them get the surrounding subconsciously in their heads.
"But when you turn up on the Sunday you are in game mode and in the zone. You cant go taking pictures of your family in the stands and all those sorts of things, on the day you are there for a specific reason.
"That is what I've learned over the years and that is what we will be trying to do - to get them into that zone."
When they kick-off at Wembley it will have been 13 days since their play-off final second leg victory over the Blades but Johnson says that long gap has certainly not been a negative when it comes to preparing his side.
"You have to make sure you use the long 13 day gap," he said. "That wasn't too bad as we needed a couple of days to get over that (the semi-final win) and the boys needed a few days away from each other really to mentally and certainly physically relax.
"And that gave us enough time to give them a few days off and then have them back in game mode."
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