What do you lead? There is no point in leading your singleton as you do not want ruffs. Your trumps are strong and will always make 2 tricks. So lead a trump - dummy will only have 3 trumps and by leading a trump and continuing them when you are in with A♥, you will stop any heart ruffs in dummy. 

Note that on any other lead declarer can make 10 tricks.
If declarer wins the AS and plays AC and another club do not be tempted to ruff the club.
 

Your first task is to describe your hand shape so partner can tell if we have a fit. You bid 3S which shows 5 spades and 4 hearts and is forcing. Partner bids 4H.
　
As you have 13 HCP and partner has a minimum of 20 you know we should be able to make a slam, especially as we have a heart fit. So you bid 4NT asking for aces. Partner bids 5H showing 2 aces and we bid 6H.

AS you can see 6H is the only slam you can make. 6NT only has 11 top tricks (on the diamond finesse) and 6S has 2 trump losers. You make 6 hearts by ruffing 2 diamonds in the dummy. You can even make all 13 tricks if you are really brave - work out how.
 

South has to choose between 4♥ and 4♠

The south players all decided to play 4H, mainly because their heart suit is better. This means that partner plays it and their hand is dummy. Can you see why this is wrong? The south hand has  most of its points in the minors and it is likely on the auction that a minor suit will be led. South needs to "protect" the holdings in the minor suits by having the lead come round to him. These holdings are called tenaces.
 
Now look at all 4 hands and see that a minor suit lead will be good for declarer if south plays the hand.