Positive experience
Oh, and always, always make the crate a positive experience. It shouldn't be used for punishment, ever.
Ways to make the crate a positive experience:
Feed him in the crate.
This will not only help him to like the crate, but dogs won't potty where they eat. Oh, this brings up another point. If the crate is too big, then he may use one side for a bathroom and the other for eating or sleeping. The crate should be just big enough for him to lay down, turn around, and sit comfortably. Since he is currently a little guy, get a crate that he will still fit as an adult, but block off part of it temporarily.
Play with him, and make the crate part of the game.
My Sheltie [mix] likes to play fetch and run after toys. To make him like his crate even more, sometimes I would toss one of his toys into the crate.
You can put him in the crate at night. At first he may whine, but ignore him and he will eventually quit whining in the crate.
I had to do this with Treader.
Put a nice, comfy little blanket that has your smell on it in the crate.
Your smell will help comfort him.
The crate is useful if you go somewhere you can crate your dog up so that he can't cause any trouble. Since your Sheltie is a puppy and still learning, you need to watch him when at all possible so that you can correct bad behaviors. When you can't, he should be in his crate.