class yourclassname(models.Model)
_inherit = 'res.partner'
comments = field.Char(requited = True) # for example, I think its a Char, you have to look in original code

Hello,

You can change attributes by 2 ways,

1. From py.

Just inherit that model and rewrite field definition again and add other attributes. 

comments = field.Char(help="test11234...") 

2. From view. 

Inherit the view and change attribute by following way. ( Just an example, I added my view to show you how to add new attribute by view inheritance. Please see bold + italic lines. I have added domain attribute )

<record id="view_task_inherit_add_project_ids_domain_form" model="ir.ui.view">

<field name="name">Task Inherit Form view</field>

<field name="model">project.task</field>

<field name="inherit_id" ref="project.view_task_form2"/>

<field name="arch" type="xml">

<xpath expr="//field[@name='user_id']" position="attributes">

<attribute name="domain">"[('project_ids','in',project_id)]"</attribute>

</xpath>

</field>

</record>

<!-- ******************************* -->

Hope this helps,