Dogs view their crates as their safe havens (they are den animals). Crating can be a very positive training tool and create a feeling of comfort for a dog when used properly. It is ok for you to crate him for short periods while you are home, in fact, it would probably be very beneficial if you are just introducing the crate or still trying to get him used to it.
It's better (for your sanity and the puppy's) to get him used to it in short periods (start with just 10 mins, then work up to 15-20, and even to 30 mins every few hours or so) during the day than to introduce it for the first time at night. Because he isn't used to it, he may cry at first, hence why it could help to introduce it during the day without interrupting anyone's sleep. Use a command word when you put him in his crate, so he gets used to that. We use "Kennel up", but you can use "get in your house", "kennel", "get in your crate", etc. Once he's used to the crate, you can decrease the amount of daytime crating, or leave him out all during the day, whichever your (and the puppy's) preference is.
If you put him in for short periods of time during the day, it is ok to put a toy or treat (something you know he won't get choked on or chew up and get choked on) in his crate with him). I know lots of dog owners who put peanut butter stuffed Kongs in the crates with their dogs. You can also give him a small treat when you put him in (or especially when he goes willingly on his own). All of this helps convey positive feelings about his crate to him.
You may find that he enjoys going in there for short periods during the day to "get away from it all"...puppies get overstimulated too! If he's used to the crate by this time, you can just leave the door open and allow him to venture in and out during the day for naps as he pleases.
However, a puppy shouldn't be left in a crate too long. One, because they need to be active and get exercise, and two, because their little bladders can't hold it that long and dogs do not usually like soiling their crates (it would be like you or I wetting the bed). Be sure to take him out about every hour to make sure he potties....set a kitchen timer if you need help remembering. :)
When you have him out of the crate during the day, but you don't want him to get into anything or don't want your other dog to get too rough with the puppy, put a leash on the pup and keep him close to you in the house.
I hope this helps some. I am no expert by any means, but I am a volunteer for a local rescue, and have crate trained foster dogs before. If you have any questions, feel free to contact me. :)