Create a column for the logos, the column header name is not all that important since you’ll be mapping it. That said, I suggest
Logo URL because I think (off the top of my head) that will auto map to the logo field in Connections so you do not need to manually map it during the mapping step when importing.
The value of the logo field in the CSV file has to be a fully qualified publicly accessible URL to the logo.
You would do exactly the same for the entry photo.
Hope this helps, let me know.