Sign in into you account. Click New Import. Choose your Hubspot account. You can read instructions on how to add a connection in this article
if you need them.
Choose Companies. Then, from the drop-down menu, choose Update Existing Records (Update). Please upload a CSV file containing the names of your child and parent companies. And then click Continue to proceed to mappings.
As with all data updates, you must first select a matching field for CSV Loader to find companies in HubSpot to update. Company Name is used in this example. Please note that these are the names of Child Companies.
Other fields can be used here, but they must be unique. If you have two companies with the same name, update will result in validation errors. Another useful field for updates is the Company ID. Remember that your CSV must include a column with values for your matching field.