Will I have to manually add the first four months of the year if they weren't uploaded when I linked my bank?

Yes, you can, Janmise.

I'd be delighted to assist you and enter those missing transactions in QuickBooks Online (QBO).

But beforehand, please know that some banks let you download the last 90 days of transactions while others can go back as far as 24 months.

To enter them, you can follow the steps below to have the transactions entered into QBO.

Here's how:

1. On the left pane, go to Banking or Transactions.
2. Press Upload transactions.
3. Select Drag and drop or select files and choose the file you downloaded from your bank. Then select Continue.
4. In the QuickBooks account ▼ dropdown, select the account you want to upload the transactions. Then select Continue.
5. Follow the onscreen steps to match the columns on the file with the correct fields in QuickBooks. Then select Continue.
6. Choose the transactions you would like to import. Then click Continue.
7. Hit Yes.
8. When you accept your transactions, select Done.

I'll share this article with you if you want to know more about uploading your transactions manually: Manually upload transactions into QuickBooks Online.

For future reference, here are some handy resources to help you supervise your transactions:

• Fix bank upload errors in QuickBooks Online
• Categorize and match online bank transactions in QuickBooks Online

If you have any additional concerns about managing your transactions, please don't hesitate to include them in your response. I'll be right there to help you whenever you need it.

@janmise-yahoo-co 

You can use MT Online or one of the converter tools with a one time license (e.g csv2qbo @ $60) as a workaround.
https://www.moneythumb.com/?ref=110