Stick with it - it will get easier trust me
Never use the crate as a training tool though, if you put them in there as punishment they will not go in there off their own accord. Leave the door open and put some toys / treats in and give lots of praise when he does go in.
When i got my first Sibe, he cried for days but soon learnt that crying got him no where lol Then when i got my second sibe around 6 months later he did the same - ended up with a few sleepless nights but wouldn't swap them for the world lol.
now, my boys wander in and out of their cages all the time and will often sleep in there while i'm making tea - it's like their Den, just make sure it's comfortable and maybe leave a radio on somewhere or a ticking clock