Put a treat in the crate and encourage him to go in... do not close the door right away! Allways make going in the crate a POSITIVE thing and start out slow. Then close the door for a few seconds... open... praise... etc. etc. then go for longer.
For Ender... if we are leaving for a long period we will give him a frozen kong (banana/yogurt is his favorite)... if for a short time or at night we will give him a kong with a dab of peanut butter inside it. We also leave on music or an audiobook when he's in the crate for a long time.
Make sure your pup only has enough room to go in, turn around, and lie down. This will help him learn to hold it 'cause dogs don't like to eliminate and sleep in the same spot. But don't over do it... you can't expect a young puppy to hold it for longer than he is able. For instance... usually a 8 week old puppy can hold it for 3 hrs.
If they are sleeping (like at night) generally they can hold it longer.
If they are active or eating or drinking... they will need to go just about every 15 minutes.
With puppies, Shannon and I would take up the water at 9pm (going to bed at 10pm) to make sure she wouldn't need to go every 3-4 hours. Be very careful with this, you dont want to dehydrate you boy or girl.