N-S should reach 4♠ easily by one of many routes. The one shown is for those playing 4-card Majors. Game is high enough on this hand. The Slam appears to depend on the Trump finesse and it is good practice to avoid bidding marginal Slams at Pairs.

A Heart is the obvious lead and those that remember the Basic Rule (Count your Losers and Plan The Play before touching a card in a Suit Contract) will do well here.

You have one Spade Loser (♠ K), one Diamond Loser (♦ A), two Heart Losers (but they can be Trumped), and two Club Losers (but they can be Dumped on the ♥ AK)

Having done that analysis you can try the Heart Finesse (dumping a Club) then immediately play the ♠ A followed by a small Spade towards the ♠ QJ, and will easily make your contract.