To create a new importer, Via the ImportWP screen (Accessed under Tools > ImportWP), click on the Add New tab at the top of the screen. The import creator screen should load up showing initial fields to create the importer.
When creating and editing an importer if you are sure what any field does, if a ? tooltip is displayed beside the field label, hover over this to read a description of what it does.
Create Importer Fields
The create importer screen is a simple form created of two fields
Name the importer
Set a name so that you can find this importer on the importer archive screen.
What are you wanting to import?
Choose what type of WordPress data you want to import, such as Posts, Pages, Users, and Taxonomy Terms.
Once you have filled out all the required fields, click on the Create Importer button to finish creating the importer. If Successful you will be redirected to the next screen to setup the datasource to use your data file.