General plugins

I try to create a new module of affectation.

I use the model I found in the newmodule.zip
I've create tables I want in install.xml page.
I modified mod_form.php page : when I try to add an affectation to a course, this page appears with the field I wanted.
but I don't know how save the value in tables.

When I try to save, the view.php page is generate as normal, but it's empty !!
If I want to modify the affectation created, values I wrote are lost (of course because I haven't link with tables) but for some fields, a letter appears ...

Is anyone can inform me what I've to do ?