I'm using a different spreadsheet just so you can see. Here is the step where you match the spreadsheet headers to your Salesforce Org fieldnames.

Do this for all the fields on the spreadsheet.

First pass: always stop and show errors. Fix all the errors you can. Then: Omit erroneous records.

You'll see a screen LIKE this. Since I'm not using your spreadsheet, it isn't exactly the same, but it will look like this. Note: shows new, updates, duplicates and rejects.

Just click IMPORT.

Then: Don't forget to download the spreadsheet at the end. ALL the records, the choice at the top of the list. Do not ever skip this step. You will be super sorry if you do.