It's possible to import a CRM details file directly into a specific CRM by opening the CRM tab, selecting the CRM on the left and selecting "Import".
The import file must contain a field named "Customer Code", it then should also have a field for each of the properties.
It's possible to export the data from the CRM by selecting "Export", and update that file to make the process faster.
(Please see attached video).
For CRM imports which contain single instances (one record per customer), the Customer Code is the key for the import.
If there are multiple records for the same customer, then only the first record will be the data imported.
To check if the CRM is "Single Instance", select the config icon, and check if the "Single Instance" box is ticked.
(Only the first record in below screenshot was imported).
For multiple instance CRM imports, the Customer Code and the first field, in this case Name, are the key fields for the import. A different name will result in a new record being added.