You chose to No Bid. This is the right answer. You do not have sufficient points to take your partner to game in Diamonds, and it would be wrong to introduce a new, and not very strong suit at this stage.
After your No Bid, the other opponent also No Bids, and the bidding sequence has ended. East, who was the dealer, will play the hand, and needs to make 9 tricks to fulfil the contract of 3 Diamonds.
Opening lead comes from South. Here is that hand.
When you are dealing with a preemptive bid, you know that chances are your suits are going to be trumped fairly quickly. So a good lead in this situation is from your King and Queen. If you lose the trick to the opponent's Ace, you will have promoted your Queen for a winner hopefully on the next round.
Here are the hands of the Dummy, which is now revealed,
You now plan your strategy. The lead was the King of Hearts, which you can win. But you know you will need to lose the Aces of Clubs, Diamonds and Spades and the Queen of Hearts as no doubt they will collect that before you get a chance to throw you heart loser away.
Sort out the hand, so that you can follow the action, as I describe how to play out the hand.
My plan of action would be to start out by playing the 6 of Diamonds, which you need to put the King on, and will then lose it to the Ace in South's hand. South will then play his Queen of Hearts, followed by a small Spade, which you will play low on, and the trick will be won by the Queen of Spades in North's hand.
North will then lead the Ace of Spades, but you can trump that with a small Diamond. Now is your opportunity to get rid of your losing heart by trumping it before you take the rest of the trumps out. It also has the advantage of putting you in Dummy, so you can cash the winning King of Spades and discard one of your clubs on it. Then you lead the 7 of Spades from North. If East trumps it, you can over trump. If he doesn't trump, you trump with a low card. Then you lead Diamonds to take the rests of the oppositions' trumps out, and then play Clubs, and lose to the Ace, but after that the rest of the tricks are yours, as you have only trumps left. You will make your bid of 3 Diamonds.
We are starting a new rubber now, so that scores you 60 points below the line.
Go now to Lesson 10 on 2 No Trump