how can we make every newbie know about the rules of the community

There is a dedicated account Hive account@newbies-guide for this purpose. A important and useful articles are provided there that we all even old users should read. A great initiative I must say.
Also we should all advise every new user to start with a introduction Post with #introduceyourself tag. All introductory Posts on Hive are welcomed by Hive account@lovesniper - OCD's Introduction Post Curation Initiative. Which mentions all useful information needed to start the journey. But most importantly, the user should go through these posts and take their time exploring things around and understanding the platform very well. This are really some cool initiatives Hive Team have come up with but definitely it's a new users duty and obligation to read and go through all this.
Moreover there should be a specific newbies guide for every Hive Community, specifically designed to make new users understand that particular tribe.
Hive account@scholaris, also shared a New Users
Guide with series of articles every new user should read.
3 things Newbies should do in their first week on Hive
The Absolute Beginner's Guide to Proof of Brain
How to post like a pro - Complete guide to Markdown formatting
CCC/Abuse and Plagiarism