You should import them using contact mechanisms or use different field types (Phone, Mobile, Fax, etc) as importing the fields from the party model will just create a single value for each import.
You can store them on notes, but I do not think its possible to import notes using CSV import.
I’m just a user too and I’m working on setting up a test system for our company.
For importing multiple information you only need to have a extra line for every additional contact