In order to import notes you must follow these steps:

1. Create a new Import Rule and choose Notes. 
2. Map all the fields you need to import. 
3. Map ”ObjectTypeCode” to a field in your data source that contains information about which type of object to link. For example ”account” or ”task”. 
4. Under Relations make sure to set the ”Regarding” to the object instance you want the note to be associated with.