do not put him in for hours OR a day to start. start with a few seconds. a minute. a few minutes. 15 min's. 1/2 hr. hour. etc… slowly BUILD UP time in the crate. reward your dog for being IN the crate - not for coming OUT of the crate.
I even used the crate as part of playtime - I'd bounce a ball or toy into the crate and have the dog go in after it. toss treats in the crate. every time I brought home a new toy or treat instead of giving it to the dog, I put it in the crate so the dog would have to go in to get it. basically associate ALL good things with the crate.
you'll have to experiment with things to put in or leave out of the crate. It really depends on the dog. for example - I use a water bottle instead of a clip on bowl for water since my dog tips over bowls. I use an old comforter as crate bedding. I toss in a stuffed kong, but never leave anything that can be a choking hazard (no bones, no chews, etc).
remember, for safety, ALWAYS remove the dog's collar before crating. collar tags can become lodged in the crate wires, causing the dog distress.
it also helps to use a word for the crate. I repeated KENNEL every time my dog went in. now, I just say "tucker, kennel" and he happily RUNS in, lays down, and awaits his treat.
start slow, build up, and keep it positive.