Rails 5: Ideal model for assigning records to a list?

I am learnerings the Ruby on Rails

What best approach in model design if try accomplish this:

1. Database has records
2. Have a page where I cam select individual database records and add it to a list(iterated table)

In mine practice project http://ift.tt/2sZzWtb I have "players" model (has_many pretenders) & "pretenders" model (belongs_to players, optional: true)

Idea is am can go to players page, & add 'pretenders' to individual players.

Am dificulty understand http://ift.tt/Lb5GiF lol