Help! Adding custom fields to invoice tables

Hi, My name is Rex,
I am urgently in need of some help with adding custom fields to the invoice tables. I want to know how to go about it, as in, which files and folders i need to modify and also what i need to modify.

The fields I want to add are:

  1. Brand / Make
  2. Parts Number(s)

I want to add the above to the invoice tables.

Your quick response will be appreciated highly. Thank in advance.

This was already asked multiple times: Custom fields in partial_invoice_table.php
Please search the forum before posting.