Click on the Contacts Tab and then click on the Import Contacts link item.

Navigate to the CSV file you want to use and click on Continue to map fields button

At this stage you will need to specify whether the first row of the CSV file imported is the header information of the file (column headers) or is it part of the data itself.

Map all relevant fields as shown in the example above.

Choose how you wish to import the list - Recommended: Choose "do not import duplicate items"

Click on the Import to my list button.

For your convenience we've attached a sample CSV file that you can use to have a play.