I want to be able to make stat blocks (which I have to do by making homebrew monsters) for npc's that help my players, and for them to be able to look the stat block up on their devices. When I go to share the monster publicly, I get a message seemingly telling me that this can be accomplished without going public but I can not figure out how. Is this even possible? I'm currently printing the stat blocks out.

If your players have characters that have Joined a DnDBeyond Campaign, then they will have access to all your homebrew collection, including unpublished ones. (Definitely don't publish if you just want to share with a campaign!)

Note that they won't be able to use the Monsters search to look up your homebrew stat blocks, but they would be able to add any of your monsters to the Extras section of their character sheet and be able to see the stat block that way.

If you share a DDB campaign with them you can send them the URL for your unpublished monster and they will be able to see it because of the shared campaign.

Thank you both so much! This helps so much.

Happy to help.