You can import an audit file .csv using Get Hands From Disk.
If it isn't working for you it's possible your file is in the wrong format. Did you request it using the PokerStars lobby menu Requests > Playing History Audit?
If so and it won't import please compress
it and attach it to a Support Ticket
so that we can take a look at it for you. Without seeing the file it's impossible to tell why it isn't importing.