This are two written guides which will give you a good start:
- https://kinsta.com/blog/laravel-relationships/
- https://dev.to/karleb/eloquent-relationship-in-laravel-51jc
There's also a free episode available in the Laravel 8 from scratch series with a simple example which should give you a basic idea: https://laracasts.com/series/laravel-8-from-scratch/episodes/19
There's also a complete serie on this but its only for paid subcribers https://laracasts.com/series/eloquent-relationships
This is a good video on deeper relationships, but you should only start with this if you understand the basics https://www.youtube.com/watch?v=5s-_SnVl-1g&t=8s
Check them out and try to implement it in your project, if you get stuck and need some extra help you can always ask.