Basic Intertable managment question

Hi all.

I’m fairly new with rails and I just finished the walkthrough in the
Agile book and I am trying to make a simple application to manage my
school’s senators. First off, is there a simple way that I can include
a combobox on the senator page that will have a list of all of the
committees, another table, and I can select any number of them and have
that change (obviously) be included in the database?

Also, if anyone can explain to me where things like this might be
documented, in the RDoc or in the Agile book, I would be very grateful.

Thanks much!