For the first couple of days we would just toss handfuls of his meals into the back of the kennel just to get his head and eventually all four feet inside.
Once he was able to get all his feet inside we then worked on getting him to turn around in the kennel and feeding him towards the front of the kennel while his whole body was inside.
The next day we worked on getting him to lie down in the kennel and would only get food if he was lying down in the kennel.
The next day we worked on having him "Go to his Kennel", turn around and lie down before he would get food and to be able to do this repeatedly.
We focused on getting him in and lying down for a couple of days to make sure he was comfortable in the kennel before progressing to some more "difficult" kennel games.
These games would be great for a puppy as well to make sure that they really love their kennel. We still don't have the door on the kennel and won't be adding it until Kobi is able to stay in the kennel for extended periods of time without it. The point of this is that the door shouldn't make him feel trapped in the kennel, the door will become more of a security measure to ensure he doesn't leave the kennel when I'm not looking to reinforce that he is only allowed to exit the kennel when given his release cue, which for us is "release".