Most likely your CSV file isn't in a correct format.
It should have an email column so that mailwizz can use it as the subscriber email address.
When you try to upload a csv file in that modal window, you also can download a sample CSV file to see how your own csv file should look like.
Ah, missed this one for some reason, sorry
When i asked to paste a few rows it was because i wanted to see the delimiters from the file. An image does not show that.
So please open your file with notepad++ for examples, and copy first 10 rows from it and paste it here (make sure you mask email addresses).