You basically have to re-upload the companies again, at the same time as the deals, and have a common column in each spreadsheet that connects deals to unique companies.
Companies that you have already uploaded will should deduplicate by name or website URL, but to be 100% sure I'd suggest exporting them first with their HubSpot UID and then deduplicating the import based on that.
Let me know if you have any more specific questions.
You basically have to re-upload the companies again, at the same time as the deals, and have a common column in each spreadsheet that connects deals to unique companies.
Companies that you have already uploaded will should deduplicate by name or website URL, but to be 100% sure I'd suggest exporting them first with their HubSpot UID and then deduplicating the import based on that.
Let me know if you have any more specific questions.