The last few days have gone fast and I'm very happy to join," he added.
The Dutch teenager also described his tactical style and on-field attributes as he transitions to English football.
"I'm a player who likes to get on the ball and play forward all the time.
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I'm happy playing between the lines and I feel I have a lot of energy in my game.
I just want to win," Steur said.
Newcastle leadership welcomed the new addition, emphasizing his developmental pathway and top-tier experience in the Eredivisie.
"We're delighted to welcome Sean to Newcastle United - he's a top young prospect who has already tasted Champions League and top-flight Dutch football," Howe said.
The manager outlined long-term expectations for the midfielder within the evolving first-team squad structure.
"We see real potential in Sean and believe he has the characteristics to become a valuable player for us for years to come.
That's something we're really excited by and look forward to working with him and helping him achieve his ambitions," Howe said.
Howe credited the Amsterdam club for providing the foundations for the player's early professional growth.
"Sean is an exciting addition to our squad.
He's had an excellent upbringing at Ajax, who have an outstanding track record of producing young players," he said.
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Sky Sports News reported that Newcastle remains in advanced negotiations with Freiburg to potentially add Swiss international midfielder Johan Manzambi for a fee valued near £51 million.
