To extended the Address first we have to go in .py file (Python file) After that we have to decide where we want extended the Address and then write start to end python code to that field.
Use below .py code in python file:
In below example, I have customized .py file. You can directly copy the below python code in your .py file. -

class address_extended_places(orm.Model):
    _name ='address_extended.places'
    _order='name'

    country_id  = fields.Many2one('res.country','Country', required=True)
    state_id    = fields.Many2one('res.country.state', 'Fed. State', change_default=True, domain="[('country_id','=',country_id)]")
    parent_id   = fields.Many2one('address_extended.places', 'Parent')
    name        = fields.Char('Name', size=100, required=True)
    active      = fields.Boolean('Active', default=True)



class res_partner(orm.Model):
    _inherit ='res.partner'

    place_id_1  = fields.Many2one('address_extended.places','Place (level 1)')
    place_id_2  = fields.Many2one('address_extended.places','Place (level 2)')
    place_id_3  = fields.Many2one('address_extended.places','Place (level 3)')