The Royals will play the winner of Sheffield Wednesday and Huddersfield Town, who face off at Hillsborough on Wednesday night. The match will decide who becomes the third team to be promoted to the Premier League for next season.
Speaking after the victory, Stam was thankful his players got through such an important game.
He said: "It was a tough game. We knew it would be from the start.
"We spoke at half-time about how we could make it more difficult for them. We got a great start after the break, but then it was about us keeping on pressing them.
"We fought with everything we had. We've done that so many times this season and if you hold on like that, you will force mistakes out of people.
When asked about how it felt to advance to the playoff final at Wembley, Stam added:
"It's great to be at Wembley. I've been there in my career as a player and go there as a manager – of course it is a different stadium now – but it is fantastic.
"There is lot at stake and it is going to be a very difficult game against one of two top sides. There will be nerves on the day and we'll need to control them. We did that tonight and also took some risks as well.
If the Royals win the final on May 29, they will return to the Premier League for the first time since the 2012-2013 season.