Hi Sari, from trying this yesterday I can probably help 
When you start the import, select the āsingle fileā option, then it asks what kind of data is in your file. Youāll see notes (under activities at the bottom) which is greyed out. Once you select the primary data youāre importing against (e.g. Contacts), Notes will no longer be greyed out and you can select it. Iāve attached a screenshot for reference.
Hope this helps!
Becs
