Welcome to the QuickBooks Community forum, shair. It's nice to have a new presence joining us today. I'm here to ensure you can get past the errors so you can import CSV files to QuickBooks Self-Employed (QBSE).
To do this, I'll need to ask for a few details to ensure I can offer accurate information and resolution. May I ask about the error you encountered? Is it similar to the one in the image below?

If so, please note that this error is due to incorrect mapping of your transactions. In this case, review your transactions to ensure they are correctly mapped or classified. You can refer to the image below: 
You can also check the CSV format to ensure you can import it to QuickBooks. I'll attach an article and image for more info: Format CSV files in Excel to get bank transactions into QuickBooks.

Meanwhile, if you have encountered a different error, additional information about it will be much appreciated.
Keep me updated about this, shair. If you have more queries with uploading data in QBSE, comment them down below. I'll be sure to be around to assist you. In the meantime, keep safe and take care always!