Controller for has_many :thorugh association

I have 2 models (Users and Cursos), where a user can join multiples cursos and a curso can have multiple users, so I used a has_many :through association between them with a model called Inscripciones (only stores the user_id and curso_id).

Now I'm trying to figure out how to allow the current user join an existing curso from the index view of cursos, but I don't know if I should do this through the Inscripciones controller or what.

Also, if it has to be done through the Inscripciones controller, I can't figure out how to create this new association in the controller and also how to do it without rendering a new view (as it has no need to display a form).

Ultimately what I'm trying to achieve this:

current_user.cursos << @curso
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