This is only the start for the Polar Bear Express.

Now it is up to the Mets to keep this Amazin’ Pete Alonso train rolling.

Alonso was named the NL Rookie of the Year on Monday night by the Baseball Writers’ Association of America, becoming only the second Mets position player to win the honor. Darryl Strawberry won in 1983. Alonso finished one vote shy of being a unanimous selection.

The honor capped off a stunning year for Alonso, who set the Mets’ single-season record for homers (53), total bases (348) and extra base-hits (85). His 53 home runs set a major league rookie record.

Now comes the tougher task for the organization. What are you going to do to help Pete?

The Mets must surround Alonso with more talent so this young slugger can carry the team to the postseason. The Mets finished three games short of the second wild card.

“I’m just looking to try to be even better next year and win more games, and get to the playoffs and win a championship,’’ Alonso said Monday night. “I just want to put every single ounce of myself into winning and bringing a championship to Queens.’’

The club really had no clue how good Alonso would be heading into spring training, but to the Mets’ credit they did not hold him back like some teams do, trying to push back the free-agent clock. Now the Mets must do more. Carlos Beltran is the manager and his hitting expertise will help Alonso. That is a good start, but Alonso needs more firepower and speed to join him in the lineup.

Alonso simply needs more help so he can continue to be a dominant force. Fill in the gaps in center field and third base, and build up the bullpen.

Imagine the excitement of seeing Alonso on the postseason stage. That will be can’t-miss October theater. That is the stage Alonso was built for, a player who is doing everything in his power to get better in every aspect of the game.

Like the Yankees with Aaron Judge, the Mets get a huge financial break because Alonso, their slugger, is coming in at a bargain-basement price.

To sign a 50-home-run hitter on the open market would cost the Mets the kind of money the Wilpons don’t spend.

Perhaps Alonso can one day take home an MVP award. Certainly, with one more good year and the leadership he has already shown, he could be named Mets captain, following in the footsteps of David Wright. He is a fan favorite and has the kind of personality that has captured this city. He is fun to watch and to be around, a breath of baseball fresh air.

And he stood up to all the different tests.

Alonso was a force on the road for the Mets. He finished with a .297/.379/.610 slash line with 18 doubles, a triple, 26 home runs and 63 RBIs in 81 games on the road this past season.

When the award was announced on MLB.TV, Alonso said the first words that came to mind were, “Holy expletive!’’

Good stuff, straight from the heart. That is the Pete Alonso way. Everything about Alonso is real and unfiltered.

Funny, too, that’s what opposing pitchers said about many of Alonso’s titanic home runs: “Holy expletive!’’

Beyond all the numbers, Alonso is totally about team. He is a good karma player and easy to root for much like Judge over in The Bronx.

Judge has gotten to that postseason stage, a place where Alonso needs to be next year.

“I hate losing and I love to win,’’ Alonso explained after taking home the hardware. “I just love to compete.’’

Then there is: The 10 percent of his Home Run Derby winnings that Alonso donated, $50,000 each to the Stephen Siller Tunnel to Towers Foundation and the Wounded Warrior Project. He also was behind the First Responder cleats the Mets wore on 9/11.

Pete Alonso did his job in explosive fashion and with pure passion, now the Mets and Brodie Van Wagenen need to do theirs: Bring more talent to Citi Field to keep the Polar Bear Express running full speed.