Summarize the following:
Choose a crate that lets your Cavalier lie on his side with his legs stretched out, or stand up without banging his head. You should avoid an overly large cage which may not feel cozy enough for your dog. A crate that's restricted in size stops your dog from soiling the space. Give him a comfortable bed and a bowl of water. Encourage your Cavalier to investigate the crate by sprinkling treats inside the bed.  The goal is to make a cozy place for your dog to go in order to feel safe and secure. Avoid using the crate as a punishment. Place a toy or two inside, so that he begins to associate the crate with interesting things. Stay home while training your dog to use his crate. Leave the crate door open and let him enter on his own. Once he's inside, feed him a meal. While he's eating, shut the door briefly and tell him how clever he is. Open the door before he begins whining and so he doesn't feel trapped. Over time, increase how long you keep the door shut. This will get him used to being in the crate.  Avoid opening the door when he is crying or he will think that crying gets him released. Leave the door open when he's not inside so that he can come and go if he needs a safe space. If you'd like to keep your Cavalier safe and out of the way at night, his crate should be comfortable and in a quiet place. Make sure the crate is out of the way of foot traffic so people's movements won't disturb him. Get him settled in his crate and leave the room while he's not crying. Remember that your dog will need to toilet overnight, especially if he's young. Set an alarm and let your dog out to toilet every 2 or 3 hours. Make sure your dog is completely comfortable with the crate before you start leaving him alone in it. Once your Cavalier is comfortable being left alone for 30 minutes at a time, you can begin gradually increasing the amount of time he's left alone. Never make a big deal when you leave or return and always let your dog out to toilet once you come back. Never crate your dog for more than 4 hours at a time (unless it's overnight). Younger dogs can only handle an hour or two while dogs that are 15 weeks or older can usually do 3 or 4 hours.

Summary:
Make the crate comfortable. Let your dog get used to the crate. Train your dog to use the crate at night. Use the crate when you're not home.