Add subjects to my user subject. Linking two tables

I generated a user table using Acts_as_authenticated and a subject
table, and I create a join table for them to build up the
“has_and_belongs_to_many” relationship between them.

This is what I want to have:
After a user logins into the system, he can see a list of subjects and
add a subject to his list ‘user.subject’ simply by clicking a button
besides the subject.

Where do I define the method? Can I define it in the ‘login’ controller
generated by AAA plugin?

Can anyone provide some examples or tutorial related to what I am trying
to do?

Many thanks.

anyone? please help

Newb here but I’ll try to be a good ritizen.

user model must contain at minimum :has many :subjects
model subject belongs_to :user

that will start you off. Hopefully that is what your looking for, your
question was rather brief.