Make it a positive experience, starting with only a few minutes at a time at first, working your way up to longer periods of time. Put in toys or special treats that they love but only get during crate time. If they are whining or barking don’t let them out until they stop. Otherwise this reinforces to them that if they bark or whine you will let them out. Once they stop barking/whining then let them out and give them lots of praise. Never use a crate as punishment.
A puppy should only be left in a crate for a maximum of one hour per month of age. If you are going to be gone longer than that then leave them in a play pen or exercise pen or laundry room with a gate so they have more room.
Use Smart Pet Love Snuggle Puppy (available on Amazon) it is a stuffed animal dog that has a heartbeat and warming pad in it to help them not feel as lonely in their crate.
If you don’t want to use the Snuggle Puppy then you can use a microwaveable rice/flax seed bag to warm and put in their crate, it can soothe them by giving warmth like their litter mates. Just make sure that they have room to get away from it if they get too warm. I also use this after their bath to help them stay warm.
The first few nights with you they will be scared and need more reassurance and patience. I like to put their crate on a chair by my bed. This way if they are whining or crying during the night I simply reach into the crate and pet them for a few minutes. They usually calm down pretty quickly. If they are persistent then take them out to the bathroom, then straight back into the crate. After they adjust to being in their new home you can work on moving the crate away from your bed.