Documentum forms for document

I have a requirement that where the user want to save some 40-50 attribute for one custom type. we have to approaches to acheive this

1. create custom attributes to this custom type and save it in docbase -- but client want these attribute values to be saved in external database

2. Use a form and associtate it with custom type and save the user inputs to external database in the form of xml file.

We have created one form and successfully installed it. Now i don't know how to associate this form to custom type documents.

2. how to save the data xml (with user inputs) file in external database on click of submit button

I searched for tutorials on form builder but didn't find any....the max i was able to understand about forms is it can be used with workflows how these forms are associated with the document that i am not able to understand

Can anyone suggest a way to integrate the forms and document object attributes or If anyone has any tutorial on forms please share it