If the lead list you just imported contains no data, it simply means you inadvertently skipped the "Mapping" step in importing your leads. Mapping tells Open Leads where to put the imported field data. Once you have chosen your CSV file to impport, you will see a screen with a list of each of the fields that are contained in the CSV.
To map the fields from your import file to the fields in Open Leads by clicking on the field and choosing your Open Leads fields from a dropdown list. If you do not have a field that matches up with the data you are choosing to import, you can click on the "Add Field" link and create a new field instantly. Click here for instructions.
If you have imported blank leads, you will need to delete them and re-import your file. When you delete the blank leads use the Filters available on your Leads tab to select leads as follows "Source" is "Import" + "Date Added" is today + a field filter for one of the common fields you use that is empty - i.e. "Field: Last Name" is empty. This should return a list of the blank leads you just imported. Then choose "Delete" from the "Apply to" dropdown menu on the far right of the Leads list, just above the Types column.
Click here for information on using Filters