Lets suppose you have model A defined as below:

from odoo import fields, models, api, _

class A(models.Model):
    _name = 'A'

   field_name = fields.char(string='Provider')

So you will inherit the model and override the field as below:

from odoo import fields, models, api, _

class A(models.Model):
   _inherit = "A"

   field_name = fields.char(string='New Name')