When contacts are loaded in bulk in a file you will have the opportunity to add the contacts into one or more Mailing List and/or to tag those contacts to indicate a particular interest or characteristic.
You will be presented with a list of Mailing Lists, and you can choose which ones the contacts should be adding into.
You cannot create the mailing list at this point, if you don't see the one you want then stop importing, create the mailing list and then start the file import again.
Any existing tags will be shown to you and you can choose the ones to use by clicking with the mouse. More than one tag can be selected, and the selected tags will be indicated with a green background.
If the tag you want to use does not exist at this point it can be created.