Hi Kevin, where can I find this addon that you found? I'm facing the same problem. Found a few custom-field type addons, but not sure if they are the correct ones, do you have a link?

you might want to create a custom module. read the docs\ https://www.odoo.com/documentation/8.0/howtos/backend.html 

You can request a customization from an odoo expert or try your own.

The rough idea is like this 

create a python file

from odoo import models, fields

class NewModel(models.Model):

    _inherit = 'res.partner'

    fdurcc = fields.Char(string="FDURCC")

And create the xml file

<?xml version="1.0" encoding="utf-8" ?>
<odoo>
    <data>

<record id="res_partner_fdurcc" model="ir.ui.view">
    <field name="name">fdurcc</field>
    <field name="model">res.partner</field>
    <field name="inherit_id" ref="base.view_partner_form"/>
    <field name="arch" type="xml">

            <xpath expr="//field[@name='category_id']" position="after">
                    <field name='fdurcc' />

            </field>

        </record>

    </data>

</odoo>

build your module and install it. There you go....         

You can only import fields, which are already available in Odoo. If you miss fields, you have to customize Odoo first and add these fields. This can be done by creating a module as described by Kevin, or by using other means, see https://www.odoo.com/forum/help-1/question/crm-133521. Creating custom fields and importing data are different topics which are not related.